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ITA5A i:ECHKX:CAL TRANSI^ATXON . NA3A TT F-15-,702. 



SPXNAL INJURY AJ^TER EJECTION 
R. Auffret and R.P. Delahaye 



Translation of "Lesions Vertebrales apres Ejection," 
Laboratoire de Medecine Aerospatiale, Centre d'Essais 
en Vol, AGARD-ASMP Working Group on Spinal Injury after 
Ejection, Report, May 197^, 99 PP. 







NATIONAL AERONAUTICS MD SPACE. ADMINISTRATION 
IfASHINtJTON,. P,CV. 205^6. JUNE. 1974 



STANDARD TITLE PAGE 



1. R«port No 



. K«port No. 

NASA ITf F-15,702 



2. Oovernmenl Accession Nq* 



4, Titlo and Subtitia 

SPINAL INJURY AFTER EJECTION 



3. Recipient's Catolog No. 



5. Report Dote , 

June 197^ 



6. P«rf0fminfl Organization Coda 



7. Author(,)f^_ Auffret and R. P. Delahaye 
Center for • In-Pllght Testing, Br^tlgny- 
sur-Orge, and B^gih Military Hospital, 
Salnt-Mandg, Prance ■ 



Q. Parfarming Organization Report Na. 



10. Work Unit No. 



9, Performing Orgontzotion Name and Address 

Leo Kanner Associates, P.O. Box 5l87, 
Redwood City, California 9^063 



1 1 . Controct or Gront No* 

NASw-2481 



13. Typo of Report and Period Covered 

Translation 



12. Sponsoring Agency Name ond Address 

NATIONAL -AERONAUTICS AND SPACE ADMINIS- 
TRATiQN, WASHINGTON, D.C. 20546 



14, Sponsoring Agency Code 



\5. Supplementary Notes 



Translation of "Lesions Vertebrales apres Ejection,"' 
Laboratoire de Medeclne Aerospatiale, Centre d*Essals 
en Vol, AGARD-ASMP Working Group on Spinal Injury after 
Ejection, Report, May 197-4, 99 PP. 



16. ,Abstroct Ejection statistics obtained from the air 
seven nations are" analyzed, including figures , on 
of death, the incidence of fracture and multiple 
preferential fracture sites. A basic review of 
the spine is followed by a discussion of the mec 
spinal fracture. It is difficult to determine t 
ejection at which fractures are most likely to o 
sion from the aircraft or landing — but the pos 
pilot at the moment of ejection is considered tg 
Importance. A study of x-ray procedure deals in 
the appearance of spinal fractures of varying de 
characteristics distinguishing them from congeni 
ties or the effects of disease. Treatment proce 
viewed, and the systematic use of x-ray exami-nati 
mended. Finally, current standards fof aircrew 
discussed, with the conclusion that in. general, 
.ar e excessively strl^LL. 

17. Kay Words (Selected by Author(s)) 18. Distribution Statement 



Unclassified - Unlimited 



forces of 
the. incJjieLn.ce 
fractures, an^ 
the anatomy of 
hanics of 
he stage of 
ccur — expul- 
ition of the 
be of prime 
detail with 
gree and the 
tal abnormali- 
dure is re- 
on is recom- 
fitness are 
these criteria 



19. Security Clossif. (of (his f-(port) 

Unclassified 



20, Security Cloisif. (of this page) 

Unclassified 



31. Mo. of Paget 

93 \ 



22. Price ■ 



NASA-HQ 



■ TalJile^ oT .Co:rxt.en:.ts.. 

" ' Page 

CHAPTER r, STATJ^STICAL STUD^ OF EJ^ECTIONS 1 

CHAPTER rr. jytECHANI^M O'F OCCURRENCE, QF SPENAL FRACTURES 13 

CHAPTER rir. CLINICAL AND RADIOLOGICAL STUDY OF SPINAL 

FRACTURES' 37 

CHAPTER IV. ■ TREATMENT OF S?INAL FRACTURES IN EJECTED 

PILOT 5^ 

CHAPTER V. PERSONNEL SELECTION ^^ 

REFERENCES . 79 



11 



Figure Captions 

1. Statistics on ejections studied (210 fradtures) : USAF, 
U.S. Army, PAP, GAP, HAP, lAP, and RAP. 

2. Statistics on French airborne troops, after J.M. Teyssandier 
and R.P. Delahaye (195 fractures in 1,188,155. jumps). 

3- Spinal fractures occurring with use of the same type of 
seat M.K.J-5 by different armed forces (tf.S. Army, U.S. 
Navy and the RAF). 

4. The Intervertebral disk (after? Schmorl). 

5. Morphology of a dorsal or lumbar vertebra (after Paturet). 

6. Morphology and structure of a vertebra (after Paturet). 

7. Mechanics of spinal fractures (after Watson-Jones). 

8. Acceleration as a function of time. Ejections using two 
different seats (MK 4 Standard and AM 6 Rocket). (Meas- 
urement of acceleration at the level of the seat, the 
pelvis, the head and the -vertebrae: ) .Ejected weight: 
seat + pilot = 172 kg. 

9. Resonance of a human body subjected to 5 and 11 Hz 
vibrations (PO = natural frequency) (after Coermann). 

10. Accleration curves with several types of cushions (after 
Latham) . 

1. Parachute, Inflatable liferaft and water-filled cushion. 

2. Parachute and thin felt cushion. 

3. Parachute and thick felt cushion. 

11. Ejection through a canopy using an MK 4 seat. Recording 
of rates of acceleration. 

12. Limit rate of descent of a parachutist in free fall as 
a function of his weight and position. 

13. Degree of shock upon opening of parachute as a function 
of altitude (28-foot canopy). 

14. Straightening of the lumbar flexure in forced forward 
flexion of the spine. Determination of breaking ^ 
point or hinge point (after E. Forgue). 



ill 



15- Tracing of an x-ray of a subject In landing position. 
The arrow represents the direction of force on Impact 

16. The anterior bodies. 
Retromarginal hernia. 
Recent multiple fractures. 



IV 



Th.e 'wQX'kJing gPQup "Spinal injury^ laJfter' eJ"ec"tlon; Mechanism, 
diagnosis- and, Burveillance'' was created, hj- the Aerospace Medicine 
Group of the AQARD ;( Advisory l^roup, for Aerospace' Research 
and Development I at the end of i97.1* ' J.t is participating in 
the research reques^ted.by the AS"IvtF/",Blo dynamic Cdmmit tee "'headed 
by Dr. Vf.L'. -Tones-, Deputy NASA. Director, 

This research report. represents: a synthesis of current 
information on spinal injury after ejection. Its preparation 
has been facilita:ted by the receipt of foreign documents written 
in response to the quest ionnaire/w;ork plan proposed by the 
French coordinators , and accepted at the AGARD/ASMP meeting of 
September 4, 1972, in Glasgow. 

We would like to thank the various participants in the 
working group for the effectiveness of their aid. 

List of Participants in the Working Group "Spinal Injury After 
Ejection" 

President: Physician General A. P. P. Gibert 
Director of the CRMA 
5a Avenue de la Porte de S&vres 
75996 Paris Armees, France 

Coordinator: Physician-in-Chief , 2nd Class 
R. Auffret 
LAMAS 

Center for In-Plight Testing 
91220 BrStlgny sur Orge, Prance 

. "' Professor R.P. Delahaye 
Begin Military Hospital 
94160 Saint-Mahdg, Prance 

Members : 

Colonel F. Barnum, USAF 
Chief, Life Science Group/IGDSL 
Director of Aerospace Safety, USAF 
Norton APE, Ca 92AQ.9, U.S.A. 

Lt-Colonel Armin Beck, GAP, MC 

Luftwaffe Institute of Aeronautical Medicine 

808. Puratenfeldbruck 

Germar^' 



Chief HunjcLn Dy'rxa,nii,ce: Brancli'. ' 

U.§^'. hpUY'- A,eJ^onied,ica,l Re s:ea,r-ch, ■Laboratory 

■Fort Ructcep-,- ,Ala,bama 3^350,, .U.SVA', 

Capt. C:v.LV Evrins- ■■ ■ ■ 

Naval Aeros-pace :Medl"cal Res-eareli Laboratory Detachment 

Nevr Orleans-, La. 70129, U.S. A'. 

Major General ir.S'. Fuchs, CJAF, MC : 

Executive Officer 

Medical Service of the Armed, Forces 

53 Bonn-Beuel 

Zingheimstr. 5 

Germany 

Dr. Hennlng E. Von Gierke 

Chief, Blodynamics & Bionics Division 

6570 AMRL CMRBA) 

Wright-Patterson AFB, Ohio 45^33, U.S.A. 

Air Commodore C.R. Griffin 
Central Medical Establishment 
Royal Air Force 
Kelvin House 
Cleveland Street 
London W1P-6AU, U.K. 

Dr. B.H. Kaplan 

Chief Safety Design Branch 

U.S. Army Aeromedical Research Laboratory 

Port Rucker, Ala*. 3636O, U.S.A. 

Group (JCaptain J.K. Mason 
RAP Institute of Pathology 
Halton, Aylesbury, Bucks., U.K. 

Col. C.S.A. Gaetano Rotondo 
A.M. Institute of Legal Medicine 
Piazza Novelll 
Milan, Italy 

Lt-rColonel P. Symeonides, MC, HAF 
General Greek Air Force Hospital 
Kypsel^'., .A 
Athens, Greece 

Dr. D,J, Thomas- ■ 

Naval Aeros;p-ace Medical Re.search Laboratory Detachment 

Box 2-2A,a7., Machoud Station 

New Orleans-, La,. 7012-9,,. U.S.A. ' 



vl 



gpiNAL XN^U-RT AFTER EJECTION - 

R» Auffret. and' R.F.' Delahaye 

Center for In-Flight Testing, Bretigny-sur-Orge, and 

Begin Military Hospital, Salnt-Mande, Prance 

CHAPTER I-.- •■ STATTS-TIGA'L STUDY OF EJECTIONS ' /H 

This analysis deals only with modern flight' .seats.. A 
single release mechanism Can -actuator in a high or low position, 
the armrests) triggers the .automatic operation of the entire 
ejection sequence. Previous ejection systems with non-automatic 
seats, which are no longer used, offer only historical interest. 

Table I summarizes the overall ejection results obtained 
by the organizations which responded to the questionnaire sent 
out by the Working Group. In cases where the entries are 
marked only with an "x" no Information was available , (RAF, HAP). 
Standard NATO abbreviations are used for the organizations. 

FAP = French Air Force 

GAP = German Air Force 

HAP = Hellenic Air Force 

lAF = Italian Air Force 

RAF = Royal Air Force 

Table I Includes two totals: 

— total No. 1 corresponds to all the lijifiormation for all 
headings (USAP, U.S. Army, FAP, GAP, lAP) . 

— total No. 2 indicates the number of pilots with spinal 
fractures and the total number of spinal fractures 
observed in the organizations responding (USAP, U.S. 
Army, PAP, GAP, HAP, lAP, and RAP). 

Table II combines two types of data which seem to us to 
be significant: 

— the percentage of deaths in relation to the total number 
of ejections, 

— the percentage of surviving pilots with spinal fractures 
in relation to. the total number of survivors. 



*Numbers In the margins- indicate, pagination in tlie. foreign text." 



ro 



TABLE I. OVERALL RESULTS: U.S. Air Force (Col. F. Barnum), U.S. Army (Drs. Kaplan and 
Braunoler), FAF (Lt-Col. Auffret and Col. Delahaye), GAF (Lt-Col. Beck, Drs. Gapel and 
Rleder), HAP (Lt-Col. Simeonides ) , lAF (Col. C. Rotondo), RAP (Air. Com. Griffin). 



Number of 
Ejections 



Death 



Successful 

j'iEjectlon 



Number of 
Pilots with 
One Spinal 
Fracture 



Number of 

Spinal 
Fractures 



: U.S. AIR FORCE 


213 


: 45 


i 168 


17 


i 33 : 


: U.S. AHi^IY 


: 91 


: 13 


i 78 


26 


i 39 i 


: F.A.F, 


: 103 


! 11 


': 92 


20 


29 ! 


: G.A.F. 


: 171 


i 34 


: 137 : 


tk 


2k i 


: li.A.F, 


! X 


1 X 


• X ' : 


6 


12 '-. 


: I.A.F, 


100 


11 


89 i 


15 : 


27 : 


: R.A.P. 


X 


X 


68 i 


32 : 


57 i 


: TOTAL 1 : : 


678 i 


n't i 


564 i 


92 : 


*152 : 


: TOTAL 2 : : 


: 


- : 


: 


130 : 


216 : 



M 



TABLE II. 



/3 



>. Total 
Number of 
Ejections 



Death 



Pilots with 
Spinal Frac- 
tures, % (as 
a Function of 
Number of Sur- 
vivors) 



u.s.A.F. ; 


213 


; 21,1 


10 , 1 ; 


U.S.. ARlvTY = 


91 


: 1^,50 


3^,3 


F.A.F. : 


103 


■ 10,6 


21,7 


G.A.F, : 


171 


: 19,3 


10,2 


I.A.F. 


: 100 


11 


16,8 


R.A.F. : 


X 


; X 


k7 



An examination of Tables I and II shows that deaths are 
most frequent in the USAF and GAF statistics. On the other 
hand, the frequency of fractures is higher for pilots in the 
lAP, FAP and especially the U.S. Army. 

These data permit a discussion of the existence of a 
possible relationship between the number of fractures and the 
number of deaths . In cases where there were a high number of 
fractures, there were few deaths, and where there were a 
large number of deaths, there were few fractures. This overall 
impression perhaps merits more careful attention; however 
the information received does not permit precise formulation .' ■ 
of an explanatory hypothesis. 

Spinal fractures after: ejection , .even with the use of modern 
seats, rema,in the mo'sf frequent ly eh'countered' injuries ClO to hl% 
of surviving pilots according to the armed, forces concerned). 
Study- of these Injuries continues, and an ■ effort should be 
made to- Implement all possible methods to decrease this high 
percentage. 



TABLE III. DISTRIBUTION OF FRACTURES. 



Vertebra 


usAF ; 


; U.S. 

[ Army 


; F.A.F. 


'G.A.P. 


■H.A.F. 


'I.A..F. 


R.A.F. 


[total 


■Observa- 
tions, 


= ^4 


* 


'• 


1 - 


■ 


[ 


- 


1 


1 ; 




: 


'. 


: - 


1 1 








1 : 




= s : 


; 1 






[ 1 






i 


: 3 J 




; "6 


: 1 






[ 1 








! 2 ' 




: _^7_ 


: 1 














! 1 : 




: D 
3 


: 1 




; 1 


; 1 






! ^ 


: 4 




: °4 


: a 


; 1 




; 3 






' 1 


: 6 




; "5 . 


2 . 


; 3 


; 3 


: 3 






2 


; 13 




: "6 


i '[ 


3 


; 2 


; 1 






2 ; 


9 




: "7 . 


3 ; 


2 


; 2 ] 


^ 2 




1 


1 ; 


11 




: °s 


1 ; 


6 


' 3 


' 2 




2 ; 


3 ; 


17 




: "9 ; 


fM 


2 ; 


] 


- 




1 ; 


7 ; 


lo ;■ 




: "lo ; 


! 


2 ; 




1 ] 


1 ; 




7 ; 


11 ' 


! 


: "ii i 


2 ; 






1 ' 


2 ; 


2 ; 


9 : 


16 




' "12 ; 


6 : 


3 ; 


3 ; 


2 ; 


3 : 7 : 12 • 36 : 

• « * * 



[Table continued on following page.] 



|\ 



Table III [continued] 



'Vertebra 



USAF 



,U.S. 
Army 



PAP 



GAP 



HAP 



lAF 



RAF TOTAL 



Obser- 
vations 



is ■; ^ 

is = * 


6 1 11 : 4 ; 5 

3 ; 3 ; ; 1 

: : 1 : 
1:1: : 


5 -8 : 46 : 

1 ; 2 ; 11 ; 

2 ; : ^ ; 

2 : ' ^ -\ 
: : 1 ! 




■SACRUM : 1 : : : : : : ; 1 ; 




..VARIOUS- ^ ; 
/UNKNOWN ^ ^ 


• 7 " * * 


* =8 

■ • 




! TOTAL : 

1 FRACTURES. 33 


39 29 ^ 24 ^ 12 


• . ■ ■ 

23 57 ' 217 




.NUMBER OF . 

:pilots ' 17 . 


' 26 1 20 \ 14 [ 6 

■ * • • 


* • 

15 * 32 ■ 130 

* ^ • 





Ul 



Tab-le JH: ^.liQvrs; the dl.§:tir4,l?.uti.on-.of, f^ractures by .vertebra. /5. 
Aa examl,n.a,ti.Qn, 9t 'tlxe' correepondirig. curve sIxqws. tliait .there Is: 

— a marked peak at tlxe level of D^p.-L.' .C37°C at the ■. "■■■ ■ 
s^lte); . 

— a high frequency of. fractures of the dorsal column 
Cmore than ha.lf of the total number of spinal 
fractures^ after ejectionl. 

These findings corroborate the data collected through 
examination of statistics on traumatic accidents in civil 
practice Cpuhlic throughways and transportatlo,h, occupational 
or sports accidents}. In thvestigating these, ejections it 
has been difficult, if not impossible, to determine the time 
when the fracture of the spinal column occurs, either upon 
leaving the ejectable seat or upon reaching the ground. It 
has been possible, however, for us to compare two sets of 
statistics: 

1. Ejection statistics from the NATO Armed Forces, which 
include fractures occurring upon ejection of the seat and 
upon landing (Fig, 1). 

2. Statistics on fractures incurred by airborne troops 
of the French Army, involving l,l8l,155 jumps (195 fractures) 
(see Fig. 2). ■' 

Prom a rough comparison of the two curves it appears 
certain that the acceleration of the seat as it is ejected 
is capable of resulting in the occurrence of fractures dis- 
tributed over the entire dorsal and lumbar areas. On the other 
harld, in trauma incurred in parachute operations, the fractures 
occur predominantly at the level of the single dorsolumbar hinge. 
Specific observations on' several -fracture siiites will be dealt 
with in Chapter II, on pathogeny. 

Multiple fractures (Table IV) frequently occur in ejected 
pilots C^Q pilots in 92, that is, 40.8^), with a virtually 
Identical distribution in the USAF, the FAF, the GAP and the 
RAF. It should be noted that a multiple fracture of the spinal 
column does mot. ;neces.sar|:ly constitute a serious .factor here. 
The energy absorbed is distributed over several vertebrae which 
show less severe injuries than if only one vertebra had been 
fractured. This finding does not seem to be a universal rule, 
however. 



/6 




£:iim 



Pig. 1. Statistics on ejections studied (210 fractures): USAP, 
U;.:S. Army, PAP, GAP, HAP, lAF, and RAP. 



Key: !• Number; 2. statistics on automatic seats 




Pig. 2. Statistics on French airborne troops, after J.M. Teys- 
sandier and R.P. Delahaye (195 fractures In 1,188,155 jumps). 



Key: 1. Number 



TABLE IV. 



/8 



Army 



Number of Pilots 
with Multiple 
Fractures 



Number of Pilots 
with Fractures 



: U.S. Air : 
: Force ; 


9 ' 


17 


: F.A.F. 


''. 7 


20 


: G.A.F. 


\ 6 


i 14 


: I.A.F. 


'i 3 


! 15 


; R.A.F, 


i 15 


i 32 



The distribution of multiple fractures (Table V) shows /9 
that an infinite variety of combinations exists. It is difficult 
to confirm the presence of any preferred combinations related 
to the anatomical physiology of the spine. Nevertheless, there 
are. frequent combinations ^'of: 

— multiple dorsal injuries, 

— fracturies In the area between Dq^i and L^* which may be 
isolated, from or associated with other sites.' 

It should be, noted that spinal fractures may occur' at 
different sltes' wi-th the same type -of seat^^ depending on >• 
the aircraft used and the operational use. (A curve drawn from 
the B,H. Kaplan report .is very meaningful on this poMt..) (Fig. 30 



H 
o 




Pig. 3- Spinal fractures occurring with use of the same type of seat M.K.J-5 by 
different armed forces (U.S. Army, U.S. Navy and the RAP). 



Key: 1. Number; 2. level of fracture; 3- lumbar 



TABLE V. 



/lO 



• 


JU.S.A.F 


F.A.F. 


: G.A.F. 


; i.A.F, ; 


R.A.F. 


h - s - s 






: 1 






4 


1 










f5-\-°5-"6-°9-°tO 


: 


: 


; - 


: - ' 


1 


;D3-B4-B5-D^ 


: 1 


: 


! - 


: - 


- 


:°4 - "5 

* 


: 




: 1 


: 


- 


!"5 - "6 


• 1 




: 1 


; _ 


- 


'4 


: - 


: 1 


: 


: 


_ 


f« - 


: - 


: 


: - 


: 


1 


i-'e - "-2 


: - 


: 1 


: 


: 


- 


f 6 - "9 - ^0 - "11 


: - 


: 


: - 


: 


1 


':°7 - "8 


! 1 


: 1 


: 


: 


- 


:°7 - "8 - °9 

>• 


'. 


\ - 


\ 


[ 


1 


l;^7 - ^8 - ^12 - ^1 


\ 


\ 


\ - 


: 1 


- 


1:^7 - °8 - °10 - ^11 -^2 


- 


\ 


; i 


] 


- 


• 




1 


: 


; " ; 


: 


1* 


! - 


- 


' 


- 




;^ - ^2 


' - 


- 


- 


\ - \ 




;S - ^0 -^1 - ^2 


- ; 


- 


1 


- '. 




:^io. ^11 -^1 ; 


- : 


1 


- : 


: 




Kl - ^2 


1 : 


: 


; 


: 




;°ii - ^12-h : 


1 ! 


: 


: 


: 





[Table continued on following page.] 



11 



Table V [continued] 



USAF 





°i2 


-^ 




: 




* 


\ 


-S 




: 




* 


''I 






: 2 






i-i 


-"-a 




! 




h- 


L 

2 


-s- 


H 


- 




iLj- 


b 






- 




h- 


^4 


-L5 - 


sacrum 


1 




! 

\ TOTAL : 




■ 


g 





PAF 

2 
1 


GAP 
: 1 
1 


lAP 

1 
1 


RAF 
: 1 : 
: 1 : 
i 3 : 


7 ; 


<^ '■- 


-^ 


t*^ 



12 



CHAgTEFt XI..'. ' MECHMycS Q'F QCCTOnEWCE D?- SFXWAI^ FRACTURES ' /ll 

1*" Anatomic: ^,eya;.ew^ 
1.-1,- Spinel 
1.2.: rintervertetircLl dls-k 

1.2..1. -jyieclxajalcal ■chaj?.aG.teriattG5- 

1.2.2.: rfutrltton 

1.2.3. Aging 

2. The meclianlcs ^ of spinal fractures ■ 

3. Physlopathogenlc mechanism: of spinal, fractures during 
ejection 

3.1- General remarks - . 

3.2. Mechanics of occurrence of injuries upon departure 
of seat 

3.2.1. Role of position .of ipilot .•'. - 

3.2.2. Ejection in abnormal configurations 
3.2.3- Transmission of acceleration to the seat 

and pilot as a unit. Importance of cushion 
., 3.2.4. Specific casesr.of ejection through a canopy 

3.3. Shock upon opening parachute 

3.4. Landing 

3.4.1. Characteristics of landing of ejected pilot 

3.4.2. Pathology of landing 

In order to understand the pathogeny of these injuries, it /1|_- 
is necessary to review basic anatomic concepts on the anatomy 
of the spine and the mechanics of spinal fractures. 

1. Anatomic Review 

1.1. Spine 

The spinal column as a whole forms a harmonious S-shaped«i 
line composed oT a series of segments. 

Prom top to bottom, four parts- may be distinguished; 

— the cervical column, which is anteriorly convex; 

— the dorsal column, posteriorly convex; 

— the lumbar column, anteriorly convex; 

— the sacrococcygeal column, posteriorly convex. 

Anatomically and phy'siologlcally, the column may be diagrammed 
in the form of two segments. :se:parate.d by-- the 12th dorsal vertebra: 
the :cervicodonsal ' segment .ab.ove- and the lumbosacral segment 1 ^■ 
b elow. 



13 



. ThQ- ino.duIattQn, fpon^ Qn,e, flexure to the next is gradual 
a,ncl ■virtua,llY- .u^no:ti,cea;l5le The yertehral type .cha^racteristlc 
of each flexure ^.g- extremely^ d,istin.Gt. In the median position of 
each segment, but the transition: effaces any special charac- 
teristics' and the hinge .'\p,ej?:ee;fera.e simultaneously possess o 
characteristics -Qf the aupradjacent and subjacent, flexures. 
Vertebrae of the farthes^t projecting points Cd6, D12, LI) 
■frequently have an anterior cuneiform coAflguration. The levels 
of transition vary from one. subject to. the next , resulting in 
several varieties of flexures. 

The different segments consist of vertebrae which are 
articulated in two areas CFlg. 3)'- 

1.2. The Intervertebral Disk (Pig. 4): 

is formed of a gelatinous central nucleus, the nucleus 
pulposus, surrounded with concentric cylindrical layers of 
flbrocartllage, the annulus fibrosus. It is separated from 
the upper and lower vertebrae .by cartilage plates covering 
the vertebral facet and participating In the physiology of 
the disk. 

The nucleus pulposus is a spherical mass 1.5 to 2 mm in 
diameter at the lumbar stage, with a gelatinous consistency in 
young subjects. It may be assumed that the movement of the 
dense gelatinous part within the more fluid part contributes 
to the absorption of shock transmitted by the vertebral bodies. 

1.2.1. Mechanical Characteristics (after J.G. Peyron) 

In healthy condition, the intervertebral disk Is a highly 
effective absorber and flexible transmitter of force. 

The nucleus pulposus behaves as a hydrostatic medium, that 
Is, it distributes the forces applied to it equally in all 
spatial directions. More or less compressible, but perhaps 
capable of viscous deformation. It translates the compression 
forces received from the two adjacent vertebrae Into cen- 
trifugal force which distends the laminae of the annulus 
fibrosus, which due to Its elasticity is particularly well 
suited to dissipate this type of force. Its resistance is 
considerable. Experimentally, the vertebral bodies will 
succumb to. he^v^jr. pressure and will be. fractured; however, this 
type of, force causes no prolapse If the disks are healthy. 
The fact tha,t .it Is composed .of interlaced oblique fibers 
affords the annulus extreme resistance tt.. forces exerted in 
a horizontal, plane. On the other hand, this structure permits 
moderate: lateral Inf Jectlon Cintervertebral angulation) (J. J. ' 
Galante). ThUs a compromise Is reached between spinal ■ 
stability and flexibility. 

14 



1 -1 , 

Listel 



2 [.mprcinlc du 
nucleus pulposiis 

3 /one criblcc 




Rcbord 

vertebral posterieur 

Nucleus pulposus 

Plaque cdrtilagineuse 



/13 



Pig. 4. The Intervertebral disk (after Schraorl). 

Key: 1. Fillet 

2. Imprint of nucleus pulposus 

3- Sieve-like area 

H. Edge of posterior vertebra 

■5. Cartilage plate 



The elasticity of the perirachidlal ligaments Is due to /l4 
the fact that their collagenic fibers gradually become aligned 
in parallel as they are gradually put under stress. The 
anterior ligament is slightly more resistant than the posterior 
ligament.. (T.K.F. Taylor and K. Little). 

A study of the pressure levels within the disk has been 
performed on cadavei:' spinea. The same study has been performed 
in vivo in man by Introducing into the nucleus pulposus a 
needle with a aemiconductor sfc^ress gauge at its tip. The intra- 
nuclear pressure la approximately 1.5 times that transmitted 
to. the vertebral .fa.cet per surface unit.: Sudden increases 
in atres-s' do not seem to cause unre cord able oaci Hat ions. The 
disk serves as an excellent shock/absorber. 



15 



The .nucleus .pulposus ■. absor.b.s more i.than .l,ts.' share o-fo'vert-'i c.a i^'1.5 
pressure, while , ttue a,nnulus. fibxosua'- receives.. ' only a part 
of thla~ pres^aure., - The, .fof ce applied .per surface unit would be 
50^ .of that applied, to. the yertebral facet,, Q±-n the case of 
equal surface c area for the nucleus pulposus and the annulus 
flbros'us- In horizontal cro&s- sectlonK ■' The. forces of cen- 
trifugal dls^ten^lon applied to. the laminae .of the annulus 
have been es-tlmated at 3 to. 5 times', that transmitted by the 
vertebrae Cper surface unit); however, a portion of. this force 
is probably abs:orbed hj- the radial resistance of the cartilage 
plates- 

In vivo, the' posterior column Cformed by the articular 
processes') transmits approximately 20% of the weight, leaving 
the rest to the somatodiscal anterior column. 

These data are valid for an erect standing position. When 
an intervertebral articulation is given an inflection , the 
intranuclear pressures quickly increase by 0.7 kg/cm^ for 5° 
angulation between two adjacent vertebrae. In vivo, normal 
day-to-day movements and positions produce appreciable 
excess pressure. The multiplication factor is on the order 
of 1.2 to 2.5 for the seated position, coughing, and normal 
bending. This reaches 2.5 to 3-5 in lifting a weight. ' ■ ." 
Dorsal decubitus ■ decreases the pressure by 50^ (L. Nachemson 
and G. Elfstrom). A residual base pressure exists in the 
nucleus pulposus due to its characteristic turgescence, to 
the elasticity of the perivertebral ligaments and in vivo to 
the tonus of the perirachidial musculature. 

Measurement of the lateral convexity of a disk under 
pressure reveals the very slight nature of its deformabllity : 
the lateral edge Increases only 0.75 mm under 100 kg of pres- 
sure, with a 4 mm loss in height. In addition to bending 
movements and movements of the spine, the spinal column also 
undergoes torsion deformation, which always appears to be 
associated with the preceding types. If the vertical axis 
around which these torsion movements are performed passes 
through the center of the disk in the cervical and dorsal 
stages, it passes well to the back of the lumbar region at 
the level of the posterior axis. As a result, the lumbar 
disks are subjected to extremely heavy pulling forces (G.G. 
Gregensen and D.B. Lucas). 

1.2.2.: • Hufrlt'lQn ■ /i6 

The adult: disk, .an avascular organ-, is. nourished by. 
imbibition. The exchange is very, active; simple. :.aub stances 
such as sugar 'and urea' diffuse easily through the disk, at half 
the' rate at whlcli. they diffuse through water. 

16 



At a yery^. ea,rly; s-tage. the dj;3k :besias. to: s.How signs, pf 
lnvolutlo.n, ana tlxe, first- regresaiye. :changea are encountered 
prior to. age 20,. . .Between ages.- 20. .ana 30., .dissolution .of con- 
tinuity appears- between some laminae ;of tlxe annulus. At age 
40 the nucleus- pulpos■u■s^ begins-, to. undergo a. fibrous involution, 
losing its gelatinous and, turges:cent appearance. Its separa- 
tion from the annulus fibrosis becotnea vague. 

In 5« ■.reality,:!;, although these symptoms of disorganization 
may be detected very early In some disks, they are also very 
erratic- 

The mechanical properties of the annular disk, extensi- 
bility, residual deformation, and energy dissipation capacity, 
decrease during childhood. Beginning with age 25 they 
stablllze,^and healthy disks will undergo no further variations 
(J.J. Galante). Physiological stresses seem to offer no 
serious threat to their healthy condition. Similarly, the 
extensibility of the anterior and posterior perirachldial 
ligaments decreases In appreciable fashion until adolescence, 
but subsequently there is virtually no further decrease 
(H. Tkaczuk). 

The operation of these structures as a single unit is 
assured by: 

— the articular processes, which "bolt" the spinal 
r;((j.:i,i.-SM.fja Icolumn together; 

— the common anterior and posterior ligaments, forming 
an extremely strong continuous sheath. The opposition 
of the ligaments equilibrates the movements of the 
spinal column; 

— the Intervertebral ligaments, which firmly connect the 717 
transverse and spinous processes. These restrain the 
motions of the articular processes; 

— the paravertebral muscular masses. These come into play 
In the physiology of spinal movements by providing 
action in opposition to passive movements. They are 
able to. tolerate, pressures greater than one ton. 

The structure of the dorsolumbar ■■, vertebrae reveals their 

vulnerability. 



17 



The'. :ve.r-te.fe?;'a.i feody> corLSiats:- of a, thin layer, .g.f comp.act . 
t>one s.-ujiTQundied,. lay- a XaJTse jna^s' of ^p'oogy .bojie,' The 'trabe.Gular 
lines ;of the spongy tione .form thr.e.e sy s^ terns. :■ a horizontal- 
sys>tem, a vert-tcal system, and-mos-t importantly an. gihllque system 
consisting of a superior oblique buad,:le ancj an Inferior oblique 
bund,le which are extended on the poa.terior arch.' 

In addition to the bundles already mentioned, the posterior 
arch Includes a transverse bundle and a' U-shaped bundle (Pigs. 5 
and 6), 

Consequently the' anterior and median parts of the vertebrae 
are virtually devoid of fibers and are predisposed to compression. 
On the other hand, the. extremely tight' Intersection of'-."the superior and 
Inferior oblique bundles at the level of the insertion of the 
pedlculus arcus vertebrae Increases the solidity of this area. 
The ligament at the pedicular or posterior wall Insertion has con- 
siderable 'Influence oh the seriousness of spinal Injuries. 



Zone criblee 

. 1 



Trou vertebral 

3 ■ ■■ 
Ap. articul. inf. 

^ Lame 




5 M R 

Boiirrclct marginal Ui^ 

6 
Corps vertebral - 



Pctiiculc ' 
Ap. tr:nisv.^ 
Tith, [naniillaire ^ 



Ap. arlicul. sup. 



10 



A p. L'pineuse H 



Fig. 5- MorphologyaO;f a dorsal or lumbal:'- vertebra Cafter Paturet) 

Key: 1, Centrum 

2. yer'tebral foramen 
[Key continued on. following pa.ge.'.] 



18 



3. In,.:Cei?J:op arti;.cular proces^s 

4. Laral.na 

5- Marginal cu&fiion 

6. Vertebral body 

7. Pedlculus 

8. Transverse process^ 

9. Mamillary tube- 

10., Superior articular process-- 

11. Sfblnous process 



1 ■ . 
Ap. articul. sup. 

2 
F. oblique sup. 

3 ^ ^.«^«..-,===.-^^-^ « 

F. oblique inf. JLrs^ f 5 

Zone vascul. equatoriale 



4 
Ap. articul. inf. 




Fig. 6. Morphology and structure of a vertebra (after Paturet). 

Key: 1. Superior articular process 

2. Superior oblique fiber 

3. Inferior oblique fiber 

4. Inferior articular process 

5. Equatorial vascular zone 

2. The Mechanics of Spinal Fractures /I 9 

Numerous pathogenic theories have been proposed on frac- 
tures of the dorsolumbar vertebrae. 

According to. Watson-Jon.es, there arq; three types of 
fractures depending on the direction of the shock CFig- 7). 



. — ' Anterior "cuhe;i'fom 'fractures-^ » Here., vertical pressure 
Is exerted on a. feo-lumn with a slight anterior, flexion. The 
force is absorbed by the anterior part of the Vertebrae, which 



19 



£Li>e. Reformed Xxi a, vrecige cQ^figuipatton, The vertebrae Af.fec.ted 
are injuref^. .^.Qlely; qxx tlxe anterior part ..of the vertebral bo-dy. 
Wei:tjh,er the posterior wall nor the disks^ and Interspinal 
ligaments are affected. 

Lateral flexion of the trunk has.-, exactly the same effect, 
but In this case- the verte.bral compression Is asymmetrical, 
being greater, on the side toward- which the 'trunk is bent. By^-; 
definition these fractures, are termed s.-t'ahle ; 

— ^^ Cornminuted' fraetures ;• The force, rather than being 
vertical. Is applied in an oblique direction from top to bottom 
and from back to front. In response the spine enters hyper- 
flexlon- The angulation becomes so severe that the antercS- 
Infertor edge of the superior vertebra penetrates the upper 
surface of the subjacent vertebral body. The intervertebral 
disk Is generally torn and the ligaments are frequently ruptured; 

— Fracture-dislocations : The traumatic thrust occurs 
perpendicular to the axis of the spinal column. The trunk Is 
forced into hyperflexion while It is simultaneously drawn 
forward. The posterior wall Is always broken, 'Wlth severe 
damage to the ligaments. These fractures are extremely 
unstable and the prognosis is severe; not Infrequently, there 
are injuries to the spinal cord. 

The strength of the vertebrae has been studied In cadavers 
In numerous instances, but this type of examination is .of-, limited 
practical applicability. 

Rleunau has performed experiments on blocks of three 
dorsolumbar vertebrae still possessing their disks and ligaments. 

Subjection of these vertebral units to pressure and monaitor- /21 
Ing the subsequent deformation by front, side and three- q^uarter 
view x-rays ■ yielded the following- ■ results : ... 

— from 600 kg to 700 kg the vertebrae showed cracks and 
compression, and there was hemorrhagic sweating; 

— complete rupture occurred at pressures on the order of 
850 kg. 

In ouir opinion It is difficult to apply the results of 
these experiments to. ejection, since they fail to. take into 
account the most significant elements- in spinal biodynamics : 

— . the Important .damping role of the ■nucleus pulp os us and 
the perirachldial muscular masses:, . 

— the direction of application, magnitude and time of 
^application of the forces. 

20 




/20 



Fig. 7. Mechanics of spinal fractures (after Watson- 
Jones) . 



3. Physiopathogenlc Mechanism of Spinal Fractures During 
Ejection 



/21 



3.1. General Remarks 

Spinal fractures occur basically during two critical phases 
of the ejection process: 

— ejection of the seat^ 

— landing. 

The seat-pilot separation phase and the opening of the 
parachute will be discussed briefly since these procedures are 
not capable of producing injury except in cases of equipment 
malfunction. 



3.2. Mechanics ''.of '.'Occurrence of Injuries During Seat Ejection 

As they are ejected, all current ejectable seats produce 
acceleration compatible with the strength of the vertebral 
structures: accelerations of less th.a.n 20 g for 20 to 50/100 
of a second, producing a jolt which in practice is less than 
authorized standards: C2.50 g/s.ec) . 

Figure 8 s ^h o w s accelerat.:J.,.<?n curves'; for the IviK.if^ (Stan- 
dard) and AH 6 Crocket), seiits. 



21 






MK 4 standard seat 

Max. acceleration = 20 g 
Seat velocity = 80 ft/sec 
Rate of change in 

in acceleration = 240 g/sec 



AM 6 rocket seat 

Max. acceleration = 15 g 
Seat velocity = l60 ft/sec 
Rate of change in 

acceleration = 200 g/sec 





10 



20 



30 



40 



SO 



Fig. 8. Acceleration as a function of time. Ejections using two different 
seats (MK 4 Standard and AM 6 Rocket). (Measurement of 
level of the seat, the pelvis, the head and the 
seat + pilot = 172 kg. 



acceleration at the 
vertebrae ,"1 ) Weight ejected 



TfiQ mQ.^fc- :)-;i}portant. factor 5;a tli.e. pQgJ^flon of tixe pllQf at 

3. 2.:iv •■ Ro'Ie^ of postf j::on of FllQt . ' /22 

Manjr Invest i.gatQrs agree w±th.. Rotbado that the position 
of the body- o^s the most important pathogenic, factor in the 
mechanics of occurrence of spinal fractures. 

Any abnormal position will weaken the spinal column and 
may produce Injury, even at a rate of acceleration which would 
otherwise be tolerable. 

A large number of factors affect the position of the pilot. 

The attitude of the aircraft at the time of ejection is of 
Importance. This modifies the pilot-seat relationship. Thus 
in ejections with the head in a low position the pelvis is 
forcibly separated from the seat, even if the safety straps are 
completely fastened. Similarly, when the aircraft is tilted 
to one side during ejection there Is a lateral flexion of the 
trunk whose severity depends on the appropriateness of 
harness design. 

If the harness Is fastened too loosely there is excessive 
freedom of movement for the trunk, which bends considerably 
during ejection, resulting in major risk for the spine. 

Forward flexion of the trunk is limited by the curtain 
and by the straps. When the low-posltloned control system is used, 
Rotondo finds thatxT lexion is more marked for ectomorphlc subjects 
with a long thorax and shorter arms. Under these conditions, 
it is possible that the pilot will be unable to place his spine 
against the seatback completely and correctly during the 
extremely short period of time between triggering of the ejec- 
tion procedure and the ejection itself. 

According to the various papers consulted, the use of low 
control results in more spinal fractures than use of the 
curtain. 

The fractures occur in the spinal flexures : 

— at the dorso.lumbar hinge, /23 

— at .the center of the D^-, Dy and Ds area,, or still lower, 
at 1,3; the -vertebrae located In the middle of each 
flexure are the weakest points- in the spine.' On the 
other haind, when the pilot is .seated in correct position. 



23 



"t'h^- natural spinal curvature 'Is decreased* in n.Q'rmal 
,8ea,tQ.cl- positJ^Qix, .th.e lumtia^ lordoaia and the dorsa,! 
k.yptLos-lsr. P.f t fie. spinal column are reduced., The colunin 
thus- has;- a- tendency- to; fall tnto- a single alignment; 
:';tliis isr the optimum position for tolerating ejection. 

Radiographic sftudies using ej:ectab.le seats confirm the 
influence of several factors on dorsal spinal, flexion. 

— ■ The seat' a'djustmehf is of fuhd'aJnerit ai. importance : . The 
"low seat pazi" position has a tendency to re-establish 
lumbar curvature and to accentuate the dorsal k^yphosis. If in 
this case the legs are brought back under the seat, the lumbar 
lordosis is . corrected but i.the<",dorsal kyphosis remains unchanged. 
There is thus an angulation in the D4-D5-Dg area. On the other 
hand, when the seat is in normal position, folding the legs does 
not change the curvature of the spine. The height of the seat 
pan should thus be adjusted according to the physical type of 
the subject. This height should be proportional to the height 
of the canopy (GAF) and should be adequate so that the thighs 
remain in contact with the seat pan and the angle between the 
trunk and the thigh is 135°. From a statistical standpoint 
there are no valid relationships between physical type, weight 
and vertebral spinal Injury (Kaplan, Barman), within the limits 
permitted by medical regulations on acceptance-'of ^alrcrew personnel, 

— If the harness is too tight > especially If the anchoring 
points of the straps are in low positions, this may result in an 
increase in dorsal fle-xure depending on the physical type of 
the subject. Rapid fastening of the straps Immediately prior 

to ejection may accentuate the flexion of the dorsal column and 
may cause fractures by compression (Auffret, Serls and R.P. 
Delahaye, 1963). Some modern electable seats are equipped with 
an automatic restraint system which exerts tension at the moment 
of ejection (power retraction unit). The attractiveness of 
such systems is statistically significant for MK 7 seats, where 
it decreases the risk of fracture (GAF). However, for MK 5 
seats (U.S. Army), the advantages of this device seem to be 
more debatable. 

— The position of the head plays an important part. The /24 
head tends to bend forward, since in all circumstances the neck 
muscles are unable to. remain erect,, even with the use of a 

high control of the curtain type. This, forced flexion accen- 
tuates the degree of. flexion of the spine. Depending on the 
habitus of the subject .Csize,' length of trunk, trunk-thigh ratio), 
the point ;of flexion occurs: 

— at the level of the dorsoiumbar hinge D]_]_, .D12,. .Lii in 
endomorphs' and meaomorphs,' ■ 



— at .the level of Dg, Dj and Dg in ectomorphs (where it 
may occur In conjunction with the above). 



2k 



The;. ;eIi.niin9,t4:on ,Q,f f-Xe;xion of .the. ferunk gLf ..-the moment of 
ejection is the ^qXq njean.s- Pf eliminating the poagiblity: of ' 
spinal, fracture- .■Qj.,3, ^rmfl. 

This flexion mechanism majr be aacompanled by- rotation of 
the head. These two raovements produce. :ciomp.lex adcelerationB 
at.Vthe level of the dorsal spinal region, A helmet which is 
too heavy, poorly^ adapted or too ..vrl.de in diameter may encourage 
rotation of the upper. dorsal column when the head of the pilot 
Is subjected to the relative wind* An identical mechanism.' is 
encountered during spin, ejections, providing full justification 
for head restraint s-ystems in specific uaes (spin tests). 

— The angle between the axis of the spine and the axis 
of thrust Cor enclosed angle)' deserves special attention. 

The ideal angle should be equal or very close to 0° . Wide 
angles favor the occurrence of injuries to the spinal column: 
even in correct ejection position, the column is not aligned 
with the axis of thrust. The consequences of a wide!, enclosed 
angle are the same as those of marked flexion of the trunk. 
The risk involved is that anterior cuneiform fractures may 
become comminuted fractures. 

Most investigators find that all these consider.ations /25 
justify the severity of the admission standards required for 
combat aircraft pilots. In particular, there is reason to 
reject candidates with marked accentuation of the natural. 
dorsal kyphosis. X-rays of kyphotic subjects on electable 
seats show little change in the sagittal spinal curvature in 
the seated position, even when ejection procedures have been 
observed. The frequent presence of dorsal scoliosis in young 
adults has led us to question the possible influence of this pos- 
tural- problem on the risk to vertebrae during ejection. 
Due to the complexity of most ejection procedures, it is still 
too soon to determine the relative statistical significance of 
these postural abnormalities (scoliosis, accentuation of 
natural dorsal kyphosis). 

3.2.2'. Ejection in Abnormal Configurations 

The altitude of the aircraft may be modified. In some 
cases ejection occurs while the aircraft is upside down or 
tilted. Loss of control at a high rotation speed during rolling 
is not infrequent* The acceleration, may be linear, circular or 
angular, ' Xn these configurations,' only the harness will keep 
the pilot in his seat,. There is a risk that, the back will not 
be in contact with the .seatback, .and tha;t the bo'dy of the pilot 
will not always be in. contact with the seat .cushion. Conse- 
quently the dynajnics: of ejection will be modified. 



25 



Jji a, tj:gfit .tu-;c'nj. tlxe :a,cceleratlon produced by. the maneuver 
vri3.1 be added to. tlxe acceleration of tlie seat* Xn a low-speed 
spin In modern aircraft,: tlxe acceleration ■■;Ax"..vde.mlo.p;ed7by:bthe 
rotation of the. aircraft i^lll hurl the pilot forward In his 
harness^,- and the anchoring points.: :of this- harness' being In a 
lovr position, .the spine will be. In, fo'.rced^^flexlon This change 
In the spinal, posture, favors, the 'occurrence .of. fractures at 
the moment when the seat :1s ejected. 

These considerations Indicate that the position .of the ■ /26 
pilot should be as follows: 

— head erect, back and buttocks uniformly in contact 
with seat ; 

— straps of harness adequately tightened, but not exces- 
sively i 

— the feet may remain on the rudder bar if the seat possesses 
leg clamps. If it does not, it is absolutely imperative 

to place the feet in the stirrups i 

— the position of the seat pan should not be changed at 
the time of ejection; 

— individual equipment, especially the helmet, should be 
chosen with the greatest care. Helmets which are too 
large have a tendency to accentuate the curvature of 
the dorsal column. In addition, they are more easily 
torn off. 



3.2.3- Transmission of Acceleration to the Seat-Pilot Unit . 
Importance of Cushion 

The following example is highly representative and Indicates 
the Importance of a factor as simple, as the. seat' cushion, nj.vi,, 

During overseas flight, a pilot found it necessary to 
abandon his aircraft due to mechanical failure. For this type 
of mission, the rigid seat padding was replaced by a more 
flexible assembly including a folded inflatable liferaft on 
the seat. In addition, for reasons of personal comfort the 
pilot had added a thick synthetic foam cushion. 

The aircraft was abandoned under ideal conditions: the 
pilot placed the aircraft in horizontal flight.:.. at. an altitude 
of 2QdQ m and reduced its. speed to: 2Q.Q. knots;, he fastened his 
harness,- minutely lnsp.ect.ed^>lts-. position and even took the 
time to consult his ejection manual! 



26 



At tix.e moment :0f. eq'ectiQn,,- he. ^felt' a, sh.arp shock and 
siiortly- ;af.tQri!ta,rd, .tjeQa^e .Qonaclous of yio.lent hack pain. 

Th.e arrival on the ground was also- exceptional; there was 
no direct contact with the ground, since the parachute was 
caught In the branches^ of a tree. 

X-ray exajnlnatlon revealed a, fracture of the eighth dorsal 
vertebra - 

The nature of the landing did not play any part in this /27 
particular case. The ideal conditions, of the ejection should 
not have resulted, in Injury. The vertebral fracture was thus 
due to the modified cushion: its use distorted the transmission 
of acceleration to the pilot; this acceleration, generally 
within the limits of human tolerance, exceeded resistance 
thresholds. 

— Experimental Study 

Experimental results confirm these findings. Investigators 
have recorded accelerations during several series of experiments 
with dummies. Accelerometers were affixed to the seats and 
to the dummies at various levels (hips, shoulders, head). It 
was possible to compare several types of cushions. 

The results are convincing: 

— the difference between the acceleration curves of the 
seat and of the pelvis of the dummy varies as a function 
of the cushion used; 

— the hardest cushions give the best results : in these 
cases the two recorded curves are almost identical; 

— the rate of acceleration at the level of the hip is 
generally higher than the rate of acceleration of the 
seat; 

— in any given experiment the rate, of acceleration is 
higher closer to the head. 

-- Mechanical Theory oh the Seat-Pilof Unit 

The almpllfled mechahlcal equivalent of the ejected unit 
may be represented by two distinct masses^ connected to each 
other by a spring-damper system corresponding to the elasticity 
and damping capability of the cushion. 



27 



■ Jf .th_e spring i& extreme 17. rigid'. Cor the dajnper Is inf In- /2j_ 
Ite.I, tlie ra,t^- pf a,c.ce-leratlQn .recarded, far the pilot la 
practlca,lly Identical to. that. :for the. .seat.-. ■Any movement of 
the '.sreat res^ulta^ in a movement pf the. dummy » 

Inversely, If . the spring Is not very rigid, it is initially 
compressed, and the acceleration, is- transmitted to the subject 
with a phase difference',' This- :del'ay corresponds to the relative 
displacement of the se^t in. relation to the subject.. The move- 
ment Is transmitted only when the' spring has been compressed 
beyond its equilibrium position. In a second phase, the spring 
begins to oscillate around Its equilibrium position. The 
energy stored up by the spring during the first phase is added 
to that of the pyrotechhical cartridge. A temporary accelera- 
tion peak for the dummy is recorded. In addition, this higher 
rate of acceleration is reached in a shorter period of time: 
the rate of Increase in acceleration is Increased. 

In reality this formula is oversimplified. The dynamic's of 
the spinal column Itself modify the transmission <f>'f;.iacceleration. 

The classic diagram of Dleckman (1957) cited by R.R. Coermann 
{1962) explains the relationship between the initial excitation 
(acceleration of seat) and Its modifications; , in the human body 
(Fig. S), The human body is an assembly of suspended masses. 
Systems of springs and dampers (ligaments, muscles, intervertebral 
disks, etc.) link the principal body masses (head, chest and 
arms, pelvis and legs). 

The concept of frequency of resonance is of prime Importance, 
This factor dominates the physiological effects of vibration and 
acceleration on the human body. These effects depend on the 
frequency Imposed and the frequency characteristic of each body 
segment. There is resonance, that is, high displacement ampli- 
tudes, when the frequency of forced oscillations is equal to 
the characteristic frequency of the system (Fig. 10). 

In order to avoid overacceleration points, it is necessary 
to filter the frequency to a maximum of 5 Hz, the principal 
resonance frequency of the spinal column, pelvis and legs. 
Elastic cushions have an unfortunate tendency to amplify the 
frequency by 5 Hz (in a period of 0.20 sec), the length of the 730 
propellant phase for many types of seats. 

In conclusion, the seat cushions, should be extremely rigid. 
Comfort .is. improved by increasing the support surface area 
Ccontouring the contact .surface). The use of, flexible cushions 
remains possible.-; with it he express: conditign that they be com- 
pletely compres.sed by the ^vteight of the 'pilot alone.. . With 
these 'reservations, no changes- are introduced into, the oscilla- 
tory seat-pilot system. 

28 



F^,20H2 




TRONC SUP 



JHOflAX, . ABDOMEN 



F(,-3Hz 



H ANCHES 

Fo2~9Hz 



Force (suic t ossis) 



U l^=2T.l'.« 



Fcrr.e 
4 fSujet detour) 



8 



Pig. 9. Resonance of a human body 
subjected to 5 and 11 Hz vlbra^ 
tlons (FO = natural frequency) 
(after Coeriaann). 

Key: 1. Head 

2 . Upper trunk 

3. Arm, shoulder 

4. Spine 

5. Hips 

6. Legs 

7. Force (seated subject) 

8. Force (standing subject) 



This study shows that 
only .Officially appr.oved 
cuahiona should be used on 
seats. 

At the present time 
these problems with regard 
to' cushion type seem .to be 
well under control, since 
aurvlval-rescue kits 
are contained in extremely 
rigid envelopes, sometimes 
constructed of plastic. 

Finally, it appears 
that the limits defined 
for rates of acceleration + 
+ Gz (25 g for a period 
of 0.10 sec; jolt 250 g/sec) 
represent the maximum 
values for the pilot and 
not for the seat. 



3.2.4. 



Specific Case of 
E J e c t ion ■ Through 
a Canopy 



Under certain circum- 
stances the ejection will 
occur through a canopy. 

The force necessary 
to burst the canopy is 
extremely small In rela- 
tion to the force of ejec- 
tion. The final velocity 
of the ejected unit under- 
goes little change: a 
decrease of 0.30 to 0.60 
m/sec. 

On the other hand, 
the acceleration curve is 
disturbed. An accelera^ 
tion peak Is introduced 
which is linked to the 
.bursting of the canopy. 



29 




1_ Titc 




,^ l_ T 5tt. 



20 


^ 




3 


W^' 


10 




^ \ 


.-^ 


/^^ 






->!r7' 


'1, 


. ..J- 



HC. 



0,1 



0,1 



Fig. 10. Acceleration curves 
with several types of cushions 
(after Latham). 

1. Parachute, inflatable life- 
raft and water-filled 
cushion. 

2. Parachute and thin felt 
cushion. 

3. Parachute and thick felt 
cushion. 

Rate of acceler.atlon 

of seat . 
Rate of acceleration 

of hip of subject. 



.Th,e pressure, .of the gun 
Is; momentarily: counterbalanced 
by the resistance of the canopy. 
Pressure accumulates in the 
tubes' :of the gun. When the 
canopy is bursty the accumulated 
pres-sure is released In the form 
of a sharp:, but very brief 
shock'- 

Experimental recordings /31 
show that this shock is some- 
times' as- high as 1000 g/sec, 
but its length never exceeds 
a few- thousandths of a second. 
Consequently a 40 g peak at 
the level of the seat pro- 
duces only 21 g for the pelvis 
and 38 g for the head. Com- 
pression of the vertebrae 
Is moderate: 2.25 KN, that 
is 225 Kg (Pig. 11). 

The acceleration is trans- 
mitted from the pelvis to the 
head In 3/100 sec. If the 
length of the acceleration 
is shorter than this value, 
the head will undergo accelera- 
tion while the vertebral com- 
pression will be smaller. 



Inversely, for greater 
periods of acceleration, 
all the damping systems are 
restrained and the vertebrae 
undergo compression F = my. 

The work of J. P. Stapp 
has shown that any accelera- 
tion less than 0.01 sec and 
80 g entrains no risk for a 
normal spinal column in 
satisfactory position. 



/32 



The acceleration point pf 
ejections through a canopy 
limits: the' thickness of conventional plextglas-s: canopies to 
9 m [sic].. In order .to. .decreets e this- acceleration peak, 
current research is- at.t.empting to. produce pyrote.chhieal systems 



30 




Fig. 11. Ejection through a canopy using an MK 4 
seat. Recording of rates of acceleration. 

Key: 1. Compression of vertebrae 

2. Head 

3. Pelvis 

4. Seat 



designed to weaken the canopy. These devices create cracks in 
the canopy. Their powder charge should not be very high, since 
the shock wave occurs very close to the pilot and may cause 

Injmry . 

Worldwide, nearly 500 ejections through a canopy have 
been performed. The percentage of injury is not much higher 
than that for conventional ejection procedures; nevertheless 
this system is still more dangerous, especially due to the 
risk of injury by fragments of plexiglass. 

All current seats; are equipped with "canopy knasves" and 
permit such ejection procedures. This, system Is only a 
safety; device designed to gain precious; fractions. ;of a second. 

This ty^pe .of safety, mechanism is Imperat.lve. for. vertical 
takeoff aircraft. The absence of relative wind in phases of 
stationary flight does not permit correct Jettisoning of the 
canopy. 



31 



Tlie :unfQ3idtps time- '.of. a, para,ch.ute. Is a function of the ' 
filling of Itsf. canopy.- ' The. distance' ■j?eq;.ulred,- for complete, 
opening varies with the size of the parachute, but is inde- 
pendent of the s-peed of movement.. 

It ha& been experimentally determined that a. parachute must 
travel a distance 6 to 8 times- its; diameter before inflating. 
Inversely, the filling time is related to. the drop rate. Shorter 
filling times correspond to higher drop rates.- 

Drop rates at higher altitudes are much grea;ter thain those /33 
close to the ground. At-20,00.0. m the drop rate may be as high 
as 200. jTi/sec C^OO knots), while close to the ground it varies 
between ^15 and 55 m/sec (100 knots) CFlg. 12). 

At high altitudes deceleration is fast and sharp due to the 
high' drop rate.. The shock occurring when the parachute is 
opened is violent (Pigs. 12 and 13). 

At 13,000 m, the time required for slowing down is dfie 
eighth that required at 2500 m. 

The rate of deceleration is sometimes as high as 30 to 40 g. 

K.E. Plecher and J.E. Neely (I960) have reported a case 
of death occurring due to atlantQoccipital separation and 
injury to the spinal cord when the parachute was opened at 
an extremely high altitude. 

Currently injury occurs only in cases of failure of the 
mechanisms designed to prevent opening of the parachute at 
excessively high altitudes or speeds. 

None of the documents received noted vertebral Injuries 
due to the shock incurred upon opening the parachute. 

3 . ^ . Landing 

3.4.1. Characteristics of Landing of the Ejected Pilot 

During the last' .500 m prior to reaching the ground or the 
sea, the pilot should jettison a. kit which most importantly 
contains a self-inflating llferaft.. This raft remains con- 
nected to, the pilot by a strap 5 m lorig. In the most modern 
evacuation systems, this assembly -is sufficiently independent 
from the pilot so: that he is- not. forced to be occupied with 
this maneuver at the last minute.- This improvement wllll 



32 



.certainly^ decreas^e- the nunjber. ,of. yertebraX, fj?a,ctuj7e3 .of ej.ected 
ptlQts-, .siuc^ all s.tat^Qtics- maalfe.stly- stow a, highej'. frequency 
of vertehx'al coiripress^lon. for pilots-, who. have, neglected to 
Jettison this: package,' ' This- has, been explained by' ' ■ ' ■ 
the fact' that the s-urvival kit ^i'eppe&^ehta an .average of 8 to 
10 kg additional weight which- must' -be- -^a^dded to the weight of 
the pilot upon impact with the" ground. 



/3.5 




/34 



Fig. 12. Limit rate of descent of a parachutist in 
free fall as a function of his weight and position. 

Key: 1. Limit rate of descent, stable position (dive) 

2. Limit rate of descent, stable position (flat) 

3- Standard atmosphere 

4. Altitude in m 

The pilot reaches the ground under special conditions dif- /3.5 
ferent from those Of the profes'sional parachutist. Aircrew 'personnel 
will have had little training in. parachute, practice. Student 
pilots will SQinetimes make Jumps prior to certification so as 
to familiarize themselves with parachute, landing, conditions. 
However* all co.untri.ea do not make use of this type of training, 
whose value ia- moreover debatable,' since, it pre.s'ents. the risk' 
of loss, of costly' personnel. ' Furtheirmore, there is. every chance 
that ejection will occur a long time aft.er this training phase. 



33 




/3.4 



3040 



6080 



10640 ' 12160 



Pig. 13. Degree of shock upon opening of parachute 
as a function of altitude (28 foot canopy). 

Key: 1. Shock upon opening In g 

The ejected pilot chooses neither the moment of ejection /35 
nor the terrain. Not Infrequently the procedure must be 
carried out at night, under strong winds, omnuneven terrain, 
over water, etc. 

The canopy area of the parachute used Is small (in most 

cases 40 m^ rather than the 60 m2 canopy used by paratroopers). 

The speed upon reaching the ground Is therefore greater than 
that of a paratrooper. 

Psychological factors must also be taken into account. 
Most often the pilot will be particularly relaxed In the 
parachute, since he will have just abandoned an aircraft about 
to crash and has thus assured his own survival. 

There is a greater chance that his arrival on the ground, 
with muscles' relaxed and in poor position, will be traumatic. 

3.4.2.: • FathQl'Q'gy' of Landing 

Deaplte the restrictions :set. forth In the preceding para- 
graph, this- pathology is relate;d to the traumatology of the 
parachutist. The percentage of injuries attributable to landing 



34 



is;. extrePI^-ly ■ft^Sfc''' P.\H-' §li.an,n.on< estifnates it ag. .betweea 30, .and 
^Q^., 4^p.^.n4tvng QH ttLe e.J^ctt.on conditions-.; In medical investi- 
gations after e^-eotivOn, moreciYeiP../. .it .is.: frequently difficult' .to 
determine. tJie' moment .at wiiicli the. spinal, fracture, bccurred 
Cdeparture of seat, arrival on the ground), 

A tw:ofold mecJianlsm Qperates upon impact with the ground. ' /36 
There is slmultaneous-ly vertical, pressure from bottom to top 
and hyperflexion of the dors-olumbar column. 

The types of fractures observed vary: there may or may not 
be injury '^^ to the disks or ligaments,, but the' fractusie.sjare almost 
always interior cuneiform or comminute.d. Serious fractures 
with rupture of the posterior wall are rare'.'. .. ■ 

Localisation of these fractures in the D12-L3 segmen.fc.i; 
with a sharp predominance at LI may be explained by the position 
of the "hinge point." In forward flexion of the spine, the 
cervical flexure.- is reversed, the dorsal kyphosis is accen- 
tuated, and the lumbar lordosis is nullified, and then is 
reversed in forced flexion, Despite the inversion of its 
flexure, the lumbar column remains virtually vertical during 
these changes. One point remains fixed: this is the hinge 
point at which maximum flexion occurs. This level contains 
the' breaking point, which is locatedtat D12-Ll:>(Flg. 1^). 



I 



A second argument in favor of this pr.eferential , site 'is, ,; 
furnished by M.J. Teyssandier and R.P. Delahaye in an x-ray 
study of parachutists in landing position. It was possible 
to use only x-rays taken innprofile, since the opacity of the 
equipment to x-rays prevented the reading ■ of front^view x-rays, 
The results are extremely interesting (Fig. 3J5). 

The landing shock may be represented by a vector: 

— directed from bottom to top, 

— originating on the ground, 

— whose value varies with the square of the horizontal 
speed of the wind for a single parachutist. 

This vector is located in a plane which. pas..ses through 
the ankles and hips, takes in vertebral bodies D12 .to L3, 
ajid passes through. th.e posterior wall of the spine at the 
level of the dorsolumbar hinge » 



35 





Fig. l^f. Straightening of 
the lumbar .f.lexurein 
forced forward flexion of 
the spine. Determination 
of the breaking point or 
hinge point (after 
E, Porgue). 



Fig. 15. Tracing of an x-ray 
of a subject in landing posi- 
tion. The arrow represents 
the direction of force on 

impact. 



Key: 1. Breaking point 



36 



cHa?Ti:-R ix3;v ; -Qi,mi:cAh 'ahd m^wmGjicm ■stiidy of 3PXnai, f.ract.ures /38 

1. Clinical s-tudy- ■ 

l.l.- ■ Asymptomatic fractures' ■ 

1.2. Fractures^ w~ltii clinical manifestations 

2. Radiology 

2.1. Tectinlque ' ■ 

2.2. Radiological, appearance of spinal fractures 
2-2.1. Number and site of fractures 

2.2.2.. Determination of stability and Instability 
characteristics 

2.2.3. Fractures with intact posterior wall 

* Body shape 

* Appearance of angles and facet - ' ■' ' 
outlines 

* Density and structure of bony area 

* Injuries of the posterior arch 

* Displacements and postural disturbances 

* Related ■ injuries 

* Concurrent Injuries 

2.2.4. Fractures with injury of the posterior wall 

* Body shape 

* Outlines 

* Density and structure of bony area 

* Injury to ' the posterior arch 

« Displacements and postural dlsturb.ances 

* Related injuries 

* Concurrent injuries 

2.2.5. Isolated fractures of the posterior arch 739 

* Fractures of the processes 

* Fractures of the articular processes 

2.2.6. Special clinical forms 

* Fracture-dislocations 

* Fractures of the anterior body 

* Dislocations and subdislocations of the 
cervical column 

3. Differential diagnosis 

3.1. Morphological variants 

— Vertebra with cuneiform tendency 

— Lack of fusion of the vertebral bodies 

— Anterior retromarginal hernia 

3.2. Congenital abnormalities 



37 



1, CXj^ulcal StU^y ' ZM 

. Seyep^l reporting organizations^ :CHAF, XAF, FAF) note that 
tfiere are no apeclflc rules: for clinical ana radiological 
examination on'' combat aircraft, .pilots, with, spinal fractures, 
^he examination- performed Is identical to. that used for other 
types' of injuries Chlghway accidents.,- .athletic and occupational:!. 
acciddntsi. ' 'i'!:);To:'j.-t'!jh:*.eoj.-';ie"d i't o r-S' it appeared 
neces-sary to: retain the bas-ic rules,' set by the 'Class leal 
teaching of medical schools and universities in various countries, 
while recommending a few procedural variations.' 

It should be recalled that the 'USAF stipulates the pro- 
cedure to be followed in the. Air Force Manual, A.F'.M. itistnuatl 
127-2. Other air.rforces have not stipulated the steps to be 
followed but do require a given number of examinations (x-ray 
examinations, for example). 

Two types will therefore be distinguished, depending on 
the absence or presence of clinical symptoms. 

1.1. Asymptomatic Fractures 

Occurring in 15 to 20^ of the cases, these show no clinical 
manifestations. There is no pain or discomfort. Static and 
dynamic clinical tests are completely negative. 

1.2. Fractures with Clinical Manifestations 

These represent the majority of the fractures observed. 
Pain is the basic clinical manifestation in most cases. TJsually 
localized in the dorsal or lumbar segment, and more rarely in 
the cervical region, this pain may assume two principal aspects. 
Sometimes violent, it appears at the time the trauma is incurred 
or immediately afterwards. This type of pain, intermittent or 
permanent and sometimes accompanied by seizures, results in 
severe functional Impairment. In other cases, it may be so 
subdued that it initially remains unnoticed, but its Intensity 
increases and It becomes apparent a few hours after ejection. 

Clinical examination may exacerbate this pain. Palpation '/kl 
and percussion, sometimes pinpoint the site of the vertebral 
injiury. The pain produced by palpation of the spinous processes 
is sometiinea accompanied by a more or less strong contraction 
of the paravertebral musculature, ' ■ accompained by limitation 
of active or passive movements of, flexion, extension or rotation 
of the trunk.' 



38 



Neurol9Sl.c. e.x'a,nil;nati..on generally does not .reveal nerve, . 
damage, Ho-vfeyer?- Qauda, eq;ulna syndrome •' and pa,rap.legia of 
rapid ons-et. Jiaye 'tieen obs-erved. 

2.: Radiology ■ 

The use- of x-ray examination differs- from country to 
country. Some armed forces^ such as the FAF, HAF, GAF, lAF 
and RAF consider spinal x-rays Indispensable. Requirement of 
x-rays- may be noted in the documents' furnished by the GAF, lAF, 
FAF, RAF and HAF. In many cases the justification for systematic 
x-rays after ejection lies primarily in the fact that 15 to 20% 
of spinal fractures are not accompanied by clinical manifesta- 
tions. In civilian medical practice there have been many 
Instances of diagnostic failure In highway accident cases due 
to the fact that no reliable method capable of confirming the 
existence of a spinal fracture was used. 

In the USAF the use of x-rays is recommended but not 
required. The same is true of the U.S. Army. It is the 
responsibility of the flight surgeon to decide whether the 
pilot should undergo an., x-ray examination of the spinal column. 

2.1. Technique 

This is no different from the technique used for any 
spinal trauma. It seems important to recall a few basic concepts: 

— The entire spine should be x-rayed in both front and 
side views . Depending on the condition of the subject, 
the examination Is performed standing or in decubitus; 

— The slightest abnormality should prompt localized x-rays /42 
in front and side views. The x-rays are taken from the 
concave side of each segment; 

— Right and left three-quarter views permit an analysis 
of the posterior arches. 

Tomographs are extremely useful in most cases. They are 
frequently used by the FAF, GAF, lAF and RAF. Some organizations 
find that the data collected permit a. finer and more minute 
analysis of the injuries' observed. This does not .seem to be the 
case with, the USAF". The reporting officer has indicated that 
tomographs' have not been performed, for USAF pilots with fractures. 
Xii the U.S'. Army tomography Is apparently used for .sites. 
suspected to be the cause of the clinical symptomatology. . i 



39 



Jp, .^eAeraX, :-fcOTiJ9sraplia ajc^e ver-f. freq^uently requested by 
Qrfctto-peaic §upge#,p&; Xn Europe,' 3ome .medical -sctools; are- :even 
0t- ttie op.in.,iQn tiia;t th.i:s practj;:ce ■e^Iiould be' :sys tenia tic. 

' Ka'diod'y'n'ajit'l.'o" t e's t s- , ■ If permitted by: -the .condition of the 
pilot, make it possible tQ. evaluate ttie intervertebral space 
and tHe ligament ^connections. The usual motions are inclination 
in right and left lateral flexion,, flexion and extension. Dynamic 
study of the' spine 'will sometimes reveal, a pinching or a discal 
cha'sraa, an enl,a,rgemeht of the space .bet'weeh the spinous. 'processes 
(FAF, lAF). 



POSITION OP VARIOUS ARMED FORCES ON THE. USE OP X-RAY 

EXAMINATION. 



/43 



Organization 



Required Radiological Examination 



USAP 



No, but recommended if there are clinical 
symptoms . 



U.S. 


Army 


No, but recommended if ■ 
symptoms 


PAP 




Yes 


GAP 




Yes 


HAP 




Yes 


lAP 




Yes (entire spine) 


RAP 




Yes (entire spine) 



''';^i';o'':^' 



■L' (■ 'J' 



USE OP TOMOGRAPHY 



Organization 


Use of Tomography 


USAP 


Extremely rare 


U.S.. Army 


Rare Cas a function of clinical 
data) 


PAP 


yery. frequent . 


GAP 


Rare, but .of prime importance 
when used 


HAP 


Rare 


lAF 


Very, frequent : 


RAF 


Palrly .frequent 





40 



2.:2.: • •Ra,4'^o:i:Qg:$,c'a,X Appear a,n.ce: .qX gp'laar 'Fracture a ■ /4.4 

2,Z.X. "mmb'ev ajxcj. glte of fractures' - :&±^. 1) 

X-rays' and, if- tJte'jr are used, tomographs will show the 
number of injured, verte.tirae and their iocatlon. A study of 
210' .spinal fractures- of. ejected, pilots; from the various armed 
forces responding to the questionnaire, from the Working Group 
shows that the following vertebrae are Injured, In order of 
decreasing frequency; 

— the dorsolumbar hinge CD12-L1), 

— the dorsal column Cbeglnnlng with D5, with a peak at D12), 

— cervical and lumbar sites, are much-less frequent; ,; ,,., 

The frequent presence of multiple spinal fractures Justifies 
the systematic performance of x-rays of the entire spine. 

2.2.2. Determination- of Stability and.- Instability Gharacteristics 

Determination'- of -these characteristics must be of -prime importance 
in any x-ray examination, since it provides the basis for evaluat- 
ing the stabilityoor instability of the injury. There is a high 
risk of secondary displacement during the days following 
reduction and iramobiliz.ation. Nerve injuries may appear. 

The stability and instability characteristics depend on 
three principal factors: 

— the comminuted nature of the fracture , which proto.ngs 
the. healing time and- increases 'the risk -of any - attempt 
at ■ re duct ion,- 

— shattering of the intervertebral disk ; 

— rupture of the interspinQus ligament j which never spon- 
taneously detaches from the bone. 

NicoJl and Holdsworth thus distinguish two large categories 
of fractures: 

— ■ stable fractures without any risk of secondary displace- 
ment, consisting of: 

* anterior compression, 

* lateral compression, 

. * fractures ;of the posterior arch above L^* 



iil 



-^' ung't^atile: 'Sv8,Qtuve& » .su-^-cept^b-Xe .tg s.econdary exacerbation 
byocreatiAg nerye- Injurte?:, and vrhlch are difficult to 
hold In a satisfactory- reduction position. . These Include: 

* fracture-dislocations hy rupture ,of the interspinous 
llga,meht ; marlced anterior co.nipreasion and comminuted 
fractures';- 

* fracture-dl&locatlonsi' 

* fractures- of the posterior arch of l4 and L5. 

A numtier of investigators jus-tly- remark that in some cases 
It Is difficult to determine, whether the fracture Is stable or 
unstable. It is not possible to make a definite classification. 

Many orthopedists Join Rleunau in relating the concept of 
stability to the intactness of the "posterior wall," and others 
to that of the "resistance wall" consisting of the posterior 
part of the vertebral body on which are Inserted the two pedlculi-,- 
an area with extremely solid bone structure, together with its 
ligament covering. Spinal fractures may therefore be divided 
Into two groups: 

— with Injury to the posterior wall, 

— without injury to the posterior wall. 

This classification is extremely valuable in determining 
treatment methods, since radically different therapies are 
indicated for these two groups. 

Spinal fractures in which the posterior wall is not 
injured (stable fractures) are the most frequent among ejected 
pilots. Fractures with Injury to the posterior wall are rare. 
Some organizations (the RAP, for example) have not observed 
any injuries of this type in 10 years of practice. 

2.2.3. Fractures with Intact Posterior Wall (stable fractures) /k6 

In the large majority of cases the posterior wall remains 
Intact, This fact is obvious in localized x-rays. Frontal 
and sagittal tomographs confirm the impression given by the 
reading of standard x-rays. A side view inflection will 
generally show normal spacing of the spinous 'processes, thus 
confirming the Intactness of the ligaments. 

The vast- majority, of cases invo.lve. fractures of the 
vertebral body. 

These will be .described, giving consideration in turn to: 



42 



-^ the: 8;li$i,pe Qf th.e body',- ■ 

" th.e' 9,p.peai?,^ce of th;e outll,nea. .of aEacets and angles - 

— th:e density: and s-tructure of t lie. b.ony' area, . 

— Injurl.es^ Qf th;e posterior arch,'- , 

— displacements; and. postural disturbances 

— related. injuries- Cdis-ks,' ligaments; and s.oft parts), 

— concurrent injuries. 

STaape 'of Body- ■ 

Cuneiform compressions- are the most frequent, lateral com- 
pressions being more seldom in occurrence. 

to_ariterior cuneiform £ompr;es^si;o-ri is manifested by a 
decrease in the height of the vertebral body, localized in its 
anterior part. 

One or several vertebrae are injured. The same appearance 
of anterior cuneiform compression is found in all the fractured 
vertebrae. 

Profile x-rays, which are the most Informative, reveal the 
degree of compression. In most cases the flattening is slight. 
Frontal x-rays sometimes reveal an enlargement of the vertebral 
body. 

Lateral c_ompres_sl^on occurs more seldom. In a frontal x-ray, 
the height of the vertebral body is asymmetrical within the 
frontal plane. 

Appearance of Angles and Outlines of Facets _ /47 

The anterior outlines are frequently irregular. In com-r 
pression fractures the anterior corner projects into the vertebral 
outline. The fracture line is seldom visible; thus Watson-Jones 
speaks of enclosed compression fractures. 

In a number of cases the anterosuperior wedge is torn 
away and the fracture line which is thus «'isible is irregular 
or rabbeted. The anterior edge of the vertebral body is 
deformed Into an obtuse angle. 

Compression fractures are accompanied by effraction of the 
anterior part of the facets. ■ In more than 75% of the cases 
briiy the' upper J'acet is' injured . In severe trauma there will 
not infrequently be reiated injuries of two vertebral plateaus 
(especially in difficult' landings ) . 



43 



Deris: jit y 'ajid gtyucture Qt .Bonj^' 'Ar'ea.- ■ 

In, f?pa,cture£i- examined a. sh:ort .time- after' ejection, there Is 
no exten;s::lve. clxange in the .density^ or 'structure of the. bony area. 
In same cases' the 'injured portion may- have, a more or less con- 
densed appearance. 

'Kxjury^ to the Foster lor Arch' 

The posterior wall is . intact',; .but related Injiurles of the 
posterior arch may be encountered. These usually involve the 
transverse processes', virhich show lapses in continuity. 

Di'spl'a'c'eme'nt's and Postural Disturbances 

In simple compressions leaving the posterior wall.'.intact , 
the immediate effects include neither vertebral displacement 
nor postural problenis . 

Related Injuries 

The disks and ligaments are generally not affected in 
anterior cuneiform compression. However, this is not always 
the case. The nucleus pulposus may collapse the vertebral 
facet which supports it. 

Injury to a disk may correspond to severe compression. It /48 
is usually the subjacent disk which is injured. These injuries 
sometimes coincide with.jift. simple rupture of the facet without . 
compression. The median or anterior portion of the facet 
thus forms a broken line in an x-ray taken in profile. 

The Isolated disk injuries occurring in some cases are 
manifested by simple pinching of the disk without any injury 
to the bone. 

A disk ruptured in this way will not separate^lfrom the bon^. 
This type of disk injury results in the more or less rapid 
onset of arthrosis. 

Concurrent Injuries 

These injuries, which are frequent in severe trauma, 
basically include; 

— reflex aerocoly, 

— other traumatic injuries,, .fractures' of the' limbs and 
the cranium. 



Hk 



2'.:2..:4.: • '^actUyeg:' WJ-tli; Tnj'ur'y -t'Q- tlxe" P'Q's-t^ejr'l'or Wa,ll .Cuns. table 
fra,qtwre^i 

■ The': 'fyeq'uegcy of thlese: 'fract'ur'es' :l.s: very s light in com- 
parison to: tiie preceding category'. This., ty-pe of fracture Is 
much more serious-, since It exposes th,e subject to nerve Injury 
(depending on the stage,' paraplegia or cauda equina syndrome). 
This requires surgical treatment and the use of a casti^ 

Some Indication of the.. injury to the posterior wall may 
already be seen In profile x^-rays. These x-rays permit a 
study of the vertebral fragments and measurement of the 
degree of scoliokyphosis. Tomographs will reveal the number^' 
of individual vertebral body fragments and the orientation of 
fracture lines. Their use makes it possible to determine the 
degree of injury to the posterior wall. These types of 
fractures may be divided into two classes: 

— comminuted fractures in which the vertebral body is 
dislocated, 

— fracture-dislocations in which the fracture line passes 
through both the posterior arch and the vertebral body, 
obliquely from back to front and top to bottom. 

The diversity of these injuries makes It difficult to per- /49 
form any systematic study. 

These fractures will be studied under the same plan as 
that used in the preceding section. 

Shape of Body 

In comminuted fractures , the vertebral body is shattered. 
There is general deformation of the body of the broken 
vertebra, creating an angulation with the acute angle of the 
spine at this level. Anterior fragments and lateral fragments 
are expelled. 

The crushed vertebral body is generally enlarged in 
frontal x-rays. In profile, the anterior fragments clearly 
project .forward, while the more or less trapezoidal posterior 
fragments jut to the rear. 

In f r a c t ur e - di, s-lo c at ions , the fracture line,' continuing 
that reaching the posterior arch.,' travels, through the' body 
in a direction which is usually oblique, from b.ack to, front 
and top to. bott.om, generally passing through, 'the up.per third 
of the body.- It divides the injured vertebra, like a long 
bone, into; two; fragments,- an upper and a lowe'r fragment. The 
upper fragment has moved forward in relation to the upper fragment. 

45 



■ Ttie. :Qutlj;ries., Qf tlie. freLgments, In toinographlc cross sections 
are distinct,- ■ ' 

■ Density and gf ructUTe' of Bc?ny Area 

Usually normal., tfies-e- may be. altered, by a process of 
condensation. 

■ Injury to^ 'ttJQ- Fositerlor Arch; ' 

In comminuted fractures- ,-. due to the shattering of the 
vertebi?al body and the Gonsiderable displacements, the posterior 
arch is always Injured, particularly at the level of the 
articulars, which are dislocated or fractured. 

In fracture-dislocations, the oblique line continues, 
simultaneously travels through both arches and dislocates the 
articular processes, and reaches the pedicull, the isthmi or 
one of the posterior attachment or stabilization systems- 

In both types of fractures, - displacements and postural - ■. /50 
problems are considerable . 

Most orthopedic surgeons emphasize the importance of 

measuring the degree of scoliokyphosis, which is a significant 

factor in caring for the patient. This measurement is per- 
formed in several ways: 

— by the angle between the two upper and lower facets 
of the injured vertebra, 

— by the relationship between the height of the posterior 
edge and that of the anterior edge of the injured 
vertebra, 

— by the general configuration of the spinal axis, the ., 
line passing through the anterior edges generally 
describing a regular curve with a wide radius. The 
angle resulting from the plotting of this line in 
cases of spinal fracture accurately measures the degree 
of compression, that is, the degree qf scoliokyphosis. 

The latter method is preferable. 

■ Related Injuries ■ 

In these tw-o type& of fractures;- 

— The dls:k subjacent to the fractured vertebra Is broken 
or destroyed. Several dis:ka may be Injured simultaneously; 
x-rays may show them it o be obliterated or pinched. 

46 



T^r-, TExe iatep^-piAOua Itgaroent?. are. yery: .frequently .to.rni 
and the g^o^t. pe,pi5;'achW1k^l parts:, are aever^ly Injured. 

— Inj'urles to,, ttie disk and xnteraplnous ligaments: which 
do not -heal £^po^taneoualy^ will have :serloua repercussions on 
subsequent deve.lopment and problems stemming from the Injury, 
and. also on the iinmedlate development.. .' This Is a factor In 
secondary mobilization after reduction. ,' 

■ Concurrent Injuries 

Since the trauma is generally severe, the patient 
will usually have several fractures Climbs, skull, ribs, etc.). 

2.2.5. Isolated Fractures of the Posterior Arch 

These are rarer in occurrence. 

Fractures of the Processes /5X 

Projecting flat processes such as the spinous or transverse 
processes, normally protected by their muscular cushioning 
rather than by their strength, are exposed in the case of direct 
impact (upon landing in all cases). 

Fractures of the Spinous Processes 

Generally resulting from direct trauma, these are located 
principally in the cervicodorsal ■ region, accompanied by dis- 
placement of the distal fragment and bulging of neighboring 
soft parts, indicating the existence of a hematoma. 

Isolated fractures of the transverse processes also occur 
in pilots as a result of direct trauma. 

These are located almost exclusively in the lumbar region. 
The distinct fracture line is usually located on the narrow 
end of the process. There may be only one line, or it may be 
present on several vertebrae or bilateral. 

Movement in the lumbar area controlled by the 1, lumbar 
quadratus occurs in a downward direction as a general rule; 
this sudden contraction contributes to the fracture. 

Bulging of the' psoas Indicates the existence of a hematoma. 

Fractures; of t:he Articular pro ceases. ■ 

Theae: fractures/ which seldom occur in. isolate.d. form, 
result :from a heavy torsion stress with lateral, flexion of the 



47 



t]:'.un.Ic .CXa,ndJ,ng ace Went),. Th.e t^hXn a,nd. extremely, fragile articular 
prpcesges: a,r^. likely tQ. tireak aud. .come '.out pt allgninent when they 
no longer .overlap by' mare tiwjx a, .few. millimeters. 

The&e fractures.-, .which are. extremely difficult .to. diagnose 
by x-rays Crequtrtng many different, views and the use of 
tomography). J are frequently discovered only at a late stage 
of painful pseudarthros-is. 

2.2,6, Special' CJinJcaT ^orms- ■ /5.2 

These are basically fractures of the last five cervical 
vertebrae occurring in the course of -the landing phase. Identi- 
fication of these traumatic injuries', combining fractures and 
dislocations, is facilitated by the small dimensions of the 
last five cervical vertebrae, their wide range of movement, and 
the presence of relatively thick disks. The subjacent vertebra 
Is pulled by the weight of the head, which falls forward. 

Injuries to 'the nerves, spinal cord and radiculae, which 
may exist in the absence of visible radiological symptoms, 
are extremely frequent and extremely serious (tetraplegia). 

Fracture-Dislocations constitute the most frequent anatomic 
form of Injury .to the last five cervical vertebrae. The upper 
rostrum of the articular process of the subjacent vertebra 
is fractured. Instability appears. 

Fractures resulting from a hyperextensive movement of 
the head include: 

— bilateral fracture-dislocations with anteroposterior 
displacement, 

— unilateral fracture-dislocations with in-place rotation 
of a vertebral body, 

— dislocation with rupture of the vertebral ring, the 
simplest type being fracture of the pediculi. 

Fractures of the Anterior Body of the vertebra, occur -;■■,. 
less frequently in pilots. These generally result from a hyper- 
extensive movement Cease observed by reporting Investigators 
not included in this study). Rupture of the antei-ior and ' 
Inferior body of the vertebra niay appear to be only, a 
minimal bone injury,- but it. is^ generally accompanied by severe 
discoligamentary injuries-,, especially -with conjoint .occurrence 
of fracture of the articular or spinous proces:ses'. 



i\8 



■ Dji.sa'o..cafJ.;on;a' ^a'lad, -gu1ad'3;s:TQ-Qat^j:.:on,s.- "Pt %iie '.CevYXQ'^X Region ^ 
i^Iiicix occur very ;^j;"^q^uently' Xn tira^ffl.c ■-accj.dents,- h,a,ve- apt . 
been Qbs-ejpyed f^ thX$ "3^tudy, 

3. ' •Dlffer'enti:a'I PtaKnoglS: CFlg. 1^1 ZM 

A differential •diagnosis- of vertebral fractures may. be 
made for a large number of Infectious: spinal diseases, benign 
or malignant tumors, and. dj>:spla'sla or. dystrophy. In these 
cases, the radiologist receives a general orientation from the 
overall clinical, symptoms and laboratory tests. In regard to 
healthy vertebrae one should be .on the alert for: 

— morphological variations which may be confused with 
vertebral fracture, 

— changes due to a congenital abnormality or disturbance 
in the development of the vertebral body, the neural 
arch or the disk-vertebra unit. 

3.1. Morphological Variants i( 

Vertebrae will sometimes show variations in their morphology. 
The most frequent variant is the vertebra with cuneiform tendency . 
Knowledge of this variant is of fundamental importance In the abil- 
ity to confirm traumatic etiology. 

Definition of vertebra with cuneiform tendency . , In statis- 
tical stiidies of vertebral bodies with a cuneiform tendency, a 
large number of Investigators have chosen to consider the 
following in defining the cuneiform tendency of a vertebra: 

— in frontal view, differences in height of more than 2 mm 
from one side to the next, 

— in sagittal view, differences of more than 3 mm for LI 
and 2 mm for the other vertebrae between the anterior 
and posterior edges. 

The vertebra with cuneiform tendency possesses regular 
undestroyed bodies without any change in structure or density. 

The different: .vertebrae' with cuneiform tendehcy . 

. Morphologically- variant vertebrae occur frec^uently. . These 
vertebrae are preferentially: found at the center of the natural 
flexuresv.i' ■•■'.. >, ' . 



49 





i 



s 



/53 




m 



w 



TV-e^l 






The anterior bodies (after Decoulx) 



D 12 \ 
L2 \ 

Retromarginal hernia 




Recent multiple fractures 



Fie. 16, 



50 



D5,- t>6.f and P7, for tJie cjQpsa,! .column, . /5.5 

Dllj .012 and LI at the dorsQlumbar hinge. 

Changes" Due' to' DeVeXopmenf al Dlsfurbahc'es ■ 

' The' 'ab'sehc'e'o'f '': -fusion .of the vertebral- bodies 



the adult:: the "paradiscal" defect .cited by -British Investigators. 

This is a frequent abnormality. It is manifested in side- 
view' x-rays of the vertebrae of children by a distinct line 
located at the insertion of one or several corners. Such 'images 
are common up to ages 21-221 At. this age these small detached 
triangular fragments become fused with the vertebral body. 
Th^ir persistence in the adult Indicates a developmental dis- 
turbance which has prevented normal fusion. 

The degree of separation of the fragment from the vertebral 
body varies: usually it is complete, and more seldom incomplete. 
It is frequently located at the anterior and superior body of 
the vertebral body, and more seldom at the anterior inferior 
body. It is rare that the detached anterior body will be 
exactly contained within the outline of the body. It will 
either be small, atrophied and even punctlform, or will be 
too large due to excess growth and will extend beyond the 
outline of the vertebra. 

Characteristics differentiating the absence of fusion . 
of the vertebral body in the adult from anterior marginal 
fracture are the following: 

— it is separated from the vertebra by a, .distinct and regular 
rectilinear line which is much different from the 
Irregular, notched line of marginal fractures, 

— a paradiscal defect remains consistently the ssime 
without any tendency to become fused. . A marginal 
fracture, in healing, produces an irregularity in 

the curvature of the anterior surface of the vertebral 
body. 

Anterior Retr'o'marg'lna'l' Hernia 

This is a notch In the superior or inferior vertebral 

fac^f of a dorsal or lumbar vertebra. 

In a aide.-vlew x-ray, it is seen as an anterior retro- 
marginal notch' inclined slightly backward, but whose anterior 
part,; on the other hand, is usually vertical and may even' be 
Inverted slightly to the rear. 



51 



Ixi. a, frontal^ x^j^.ay-ji.ta lengthwise appearance Is that .of a /56 
PQle .Q.r cup. ■ 

This notch may he accompanied hy an .overall Increase In 
the height of the Interverte.bral aisle.- In s.ome cases, an . 
osteQphytlc excrescehce may be' noted. In,, front of the vertebral 
edge. 

This type of refromarglnal hernia Is- a variety of Int ra- 
sp ongy hernia which occurs at the level of an coiterlor 'Zone of 
least resistance In the spongy tissue of the vertebra. It Is 
frequently observed In sequels to Scheuermann's disease. It 
generally occurs In. conjunction with other characteristic 
symptoms of the disease, but Its occurrence may be isolated. 

3.2, Cdngenltal Abnormalities 

There are many types of these abnormalities and they will 
be cited very briefly. They are relatively easy to recognize. 

Rare abnormalities Include: 

— anterior rachischlsis, which should not be confused 
with a sagittal fracture, 

— congenital vertebral block, which is much more regular 
in height and shape than traumatic block, 

— the persistence of Hahn's vascular silts, fine distinct 
lines which can be seen from the side passing through 
the center part of one or several undeformed vertebral 
bodies. The anterior portion of these distinct lines 
Is especially sharp. 



52 



CHAFTER J^.: ■ TI^A^MEWT QF gFINm. FRACTURES- m Tim EJECTED PILOT ' /51 

General ComrrieiitS; 

General fherapeutlc principles; ■ 

Length, of unfitness: for service 

1. Clinical study 

1.1. Injured pilots with, unrecognized fractures 

1.2. Pilots whose. 'injuries are recognised and treated 

2. Anatomicopatholog$:cal development of fracture site 

2.1. Early-development 

2.2. Later development 

2.2.1. Bone site 

2.2.2. Disks 

3. Radiological appearance of sequels 

3.1. At the level of the bone sites 

3.1.1. Case of simple compression fracture 

3.1.2. Case of compound fractures with or without 
injury to the posterior wall 

3.1.3- Failure to heal 

3.2. At the level of the disk and the peridiscal tissue 
3.2.1. Preferential sites of pinching or gaps 
3.12.2. Peridiscal calcification 

3.3- Displaced vertebrae 

4. Sequels to ligament ary injury 

General Comments /58 

Pilots are usually examined by a flight surgeon shortly 
after ejection and in most cases are sent to an x-ray clinic, 
and hospitalised and treated in an orthopedic surgery department. 

General Therapeutic Principles do not differ from those '/followed 
in current practice, for example after occupational, traffic 
or athletic accidents. A general outline will be given cor- 
responding to the preferences of various schools of orthopedic 
surgery. 

Simple/ Compression Frac-ture " 

— Strict bedrest on a hard surface', immediately, 

— Early- rehabilitation to. the extent that the fracture 
is stable and not compound. 

53 



-r- PaJ,n cloeSi:- nQ.t .?-..eem toffee a. .contraj.ndicatlQn to 

— Fat tent ambulatory^ at tlie end pt 3 vreeks.. 
■ fracture" 'vrltK "E"riucl'eati:on 

— l\ to. 6 vreelcs' bedrest , 

— Rehabilitation beginning at a late, stage since, this type 
of fracture Is. more painful (beginning with the 3rd or 
4th week on the average) . 

Gompound Fractures 

— If there is no:: regression" In the first hour following the 
fracture, neurological complications In these cases 
are permanent. 

However, surgical treatment Is necessary to stabilize the 
fractures and permit easier nursing. 

— When there are neurologic complications, the fracture /59 
site should be stabilized by orthopedic orssurgical 

means (particularly osteosynthesis). The technique 
used depends on the type of Injury. 

Multiple Fractures 

— Heavy compression sometimes results In changes in the 
sagittal posture, especially in the dorsal region. 

The Length of Unfitness for Service , In view of the wide-- 
variety of the different types of spinal fractures which may 
be observed In ejected pilots, is difficult to determine with 
certainty. Two organizations have given precise responses to 
the editors* questionnaires (FAP, GAP). 

NUMBER OF PILOTS WITH AVERAGE LENGTH OF UNFITNESS FOR 
. . SERVICE., 

Unknown .11 2-3 6 7-8. 12 . 14-16 . 18 Perma^' 
■:'-mQ-''^-l . mQ.s..*,'*--mo.s,.:j.:;maa..; ■. .."jmo-a... . .:':'mo..s.*\.;. mo.s.viJ^.i.i ;h^nt 

GAF 1 2.2.- 6 1 2 . 

■FAF ■ 3 : 4 • 5 5 - 1 -•■ 1- ■ 1 



54 



Due .tQ. tlvej^r. freqMency-, tiies-e present problems to'- all' 
phxsiel.an.ei~ responsible for' th:e mecjlcal' .surveillance ot combat 
aircraft pilots-. 

1.^ • Clinical- gtudy 

It was possible to. divide Injured patients Into, two 
categories : 

+ ■ Injured subjects whose fractures remain unrecognized, 

subjects whose Injuries are recognized and treated, 
but who show a delayed pain syndrome, 

1.1. Subjects With Unrecognized Fractures : /60 

In most cases the fracture remains undetected due to the 
lack of any radiological testing, which justifies: 

— systematic performance of x-rays of the entire spine 
for every ejected pilot, 

— the use of a completely reliable x-ray technique, 
frequently complemented by tomography. 

Secondarily, there is the onset of pain localized at a 
fairly precise point and aroused by assumption of a standing 
position or forward bending, and sometimes accompanied by 
radicular irradiations. 

The laterovertebral muscular masses are atrophied: the 
mobility of the spinal segment involved is decreased. The 
spinous process is painful at this level. 

In some cases x-rays reveal considerable vertebral de- 
fonnatlons whose latency can only be considered surprising. 

1.2. Subjects Whose Injuries' Are Recognized and Treated,' but 
Who Show a' Belated- Fain Syndrome ' 

In these cases the subject complains of renewed pain at . 
the end of several months or years.- 

Th.e origin of these pain phenomena should be sought in- 
the ■persistence of a muscular and ligamentary. deficiency due 
to the incomplete functional rehabilitation of the patient, 

55 



vrtLQ wi;ll ngt :a,lvta,y'S tiaye undeTsto,od th;e. necessity, for this ■ 
t reati^eiat , §Qme pilqts, vrith fractures: are subject to. cervical 
or (iQ]:^aolun^lt)al:' pain during helicopter flight (U.S. Army). 

2.\;Ah.'atQmicopath.ol'Q'gicar Devel'ophierif iof' •Fr'acfure' 'gj'te 

Study of this development, facilitates, comprehension of the 
radiological image. Classrificatlon of. fractures' as: stable and 
unstable forms is extremely valuable in describing the early 
development of vertebral body fractures. 

2.1. Early Development . ' /6l 

In stable forms, .compression ■ reaches a maximum at the 
outset. There is no risk of exacerbation. Movement is 
possible at an early stage. 

In unstable forms, secondary displacements of bone, ligament 
or disk injuries, furthered by gravity, are possible at the 
least movement of the subject (transport, x-ray examinations on 
a table, or even x-rays taken with the patient remaining in bed). 
The Immediate immobilization of the patient should remain in 
force until the injury begins to heal. A bony.yor fibrous callus 
or simple fibrosis of the soft parts will appear after a 
variable period of time (1 to 3 months). 

2.2. Later Development 
2.2.1. Bone Site 

Vertebral fractures heal in a twofold manner: 

— formation of a callus at the level of the destroyed 
spongy tissue, 

— healing by periostic callus, a phenomenon which is 
certainly less marked in these cases than in fractures 
of the long bones, and whose occurrence here is denied 
by some investigators. This consolidation is mani- 
fested in x-rays by the appearance of small calcified 
fragments detached from the anterior ligament, and by 

, formation of orteophytes along the margin. 

■ The False^ Kumm'e'l"Verneuil Syhdrome 

Prior to the availability of x-ray ^teGhniq;UeB, Kummel and 
Verneull described', a syndrome characterizied. from a clinical 
standpoint by initial trauma with attenuated, and short-lived 
clinical symptoms: 

56 



-^■^ fiy. an asymptomatic interval, 

— by^ tHe ;s;ecQnd,ary onset of scoliokyphosis with resumption 
of pain. ".!:'?■ ■ ' 

They related this clinical pattern tO- secondary vertebral com- 
pression due to: post-traumatic osteoporosis. However, in sub- 
sequently reported cases of this syndrome, the absence of x-rays 
performed immediately after the trauma (during the following 
24 hours) makes it Impossible to retain a single undebatable 
case of progressive secondary compression. 

H. Mangin, R.P. Delahaye, and R. Buchet have reviewed files /62 
on 102 cases of spinal trauma occurring in the course of radio- 
logical examinations following aircraft accidents from 1951 
through 19^3. Results of x-rays performed during the 24 hours 
following the aircraft accident were compared with those per- 
formed in 1962 or 1963. There were I6 compression fractures 
and 86 traumas without any initially detectable Injury. 

In no cases did these investigators observe any vertical 
compression subsequent to the various tests performed. They 
were able to state that the techniques used, employing standard 
x-rays and tomographs, were extremely reliable, given that 
no fractures went undetected. 

At present most orthopedic surgeons and radiologists con- 
cern themselves with the traumatology itself, assuming that 
post-traumatic vertebral compression — the anatomic basis 
of the Kummel-Verneull syndrome — is not present. 

Thus we might indicate the necessity of performing systematic 
x-rays on ejected pilots, even if the clinical symptomatology is 
absent. There Is no need to emphasize that this examination 
should be technically perfect and that valuable information 
can be supplied by tomographic examination In questionable cases. 

2.2.2. Disks 

An injured intervertebral disk never recovers its original 
structure. Deprived of its elasticity, it ceases to serve as 
a hydra'ulic damper of spinal movements.- Post-traumatic cal- 
cification of the nucleus pulposus is rare. On the contrary, 
rather thain undergoing densiflcatlon and ossification, the 
disk becomes deformed: it thus permits- the vertebral bodies 
to alter their positions in relation to each other. In 
exceptional cases it may degenerate and disappea,r completely 
Ctraumatlc block!. 



57 



3".l.' ' 'At' tKe :LeYeX Qf tlxe Bone' s:xte:s: .- ; 

• 3.'!". 1'.- ' 'Ca'se' of glinple^ :c'omp'x?'e'a'sl;on: 'Fr'a'c't'ur'e ■' ' 

Cuneiform compressions- pers-l.s.f, 'There is frequently a 
discrete densification of the compressed body, but it retains 
its regular s-hape. ' This- is, th;e' phenomenon of reassimilation. 
In most cas-es the' intervertebral space retains its normal height. 

3.1.2'.' • Case- of . ■CQ'mp'o'u'nd' 'Fra'ct'u're's 'tj'i'th' or' 'vrithouf rn'J u'r'y to' the 
pQst^erjor' "tfell 

Very early marginal osteophytosis indicates the severity 
of injury to the disk. The degree of pain — which is of 
frequent occurrence — simultaneously depends on the arthrosis 
and on deficient tonus of the laterorachidial musculature. 

3.1.3. Failure to Heal 

The onset of pseudarthrosis appears in x-rays as the per- 
sistence of a fracture line; this phenomenon is very frequent 
in the vertebral processes. 

Pseudarthrosis of the spinous processes, transverse pro- 
cesses and articular processes should be pointed out in this 
connection. 

3.2. At the Level of the Disk and the Perldiscal Tissue 

The following distinctions will be made as a function of 
the anatomicopathological co.urse: 

3.2.1. Preferential Sites of Pinching or Gaps 

These tend to return the spine to an upright position. 
They can be accurately detected only by the use of radio- 
dynamic methods. 

3. '2. a.: ' peridi's-c^a,'l 'Calcification.. 

This is generally accompanied by pinching of the disk. 
One may observe;. 



58 



-■- ma,rgl.rtal oate-QphytQats^ appearing in, the. form .of a dense 
pj?Qi.4-:l' erat'^.Qn of- yei?te:tir-al edge.s: and,, angles with; regaird 
ta-th;e Injured. "vei?te.bra. ■' Th.e '.subjacent vertebra will 
usually' provl.cle a supporting :5urface;' 

— extradiacal sjrnostosls-.. In, front of or to the side of 
the vertebral body there is. a bony bridge spanning the 
dlslc and fusing two. or- three Vertebrae, spontameously 
forming a virtual verte.bral graft. 

These phenomena, howrever, are observed in the absence of 
any change in the. height of the Intervertebral spaces. The 
role of hemorrhages particularly affecting the peridiscal space 
should be kept in mind in considering the origin of these 
synostoses. 

The disk may disappear completely. In these cases there Is 
fusion of two neighboring vertebral bodies. This phenomenon is 
relatively rare. 



3.3' Displaced Vertebrae 

The disk may become deformed, permitting the vertebral 
bodies to shift in relation to each other. At the level of the 
lumbosacral hinge, the anatomic structure lends itself to 
slipping of the fifth lumbar vertebra in front of the sacral 
facet in cases of traumatic rupture of the vertebral isthmus 
(rare). Usually the trauma reveals pre-existing spondylolis- 
thesis. 

4. Sequels to Ligament ary Injury 

This concerns the failure to heal of Interspinous ligajnents 
The late onset of pain is frequent in the course of spinal frac^- 
tures. Postural changes exacerbated by the deficiency of the 
laterovertebral musculature offer more explanation for the 
persistence of pain than for the onset of arthrosis. The sig- 
nificant results furnished by kinesitherapy definitively show 
the large extent to which this pain is of muscular origin. 
In conclusion: 

The most frequent .final res:ult^ :.of spinal, fractures' is' thus 
' arthrosis . 

Whatever spinal region is. considered, radiodynamlc symptoms 
are present at a more or less: early stage,' 



59 



■ Ttle' prottlem p.'f rep^ej'af&q ej-ec't'l^orts- .;' .Mention should be . 
made ,of tlxe pQ$.Ql,tti.li.ty- .of repeated ej^ecti-ons, with, spinal 
fractures; fqr the aajije pilot,,. . If appears difficult' to. o.ffer. 
any general treatment procedure for .this problem, and the 
specialist s'^imust make iiis- evaluation as a function of ortho- 
pedic and psychological criteria, taking into account the 
length of service of the pilot, his aeronautical experience 
and his motivation. 



60 



1. Admits sion. ■ q:? a.i.rcrew ' 

1.1.- ■ Radiological test' .of, fitness- ■ 

1.-2.-, Concepts-- of . normality' 

1.3. Static dls-turbanceQ-.- Broaclened. definition of normality 

1.4 .. I^ltnes-'s^ and congenital abnormalitles' 
1.4.1.- Discos-omatic abnormalities 
1.-4.2.- Abnormalities of the posterior arch. 
1.4.3. "Eransitlonal abnormalities 

1.5. Acquired diseases and fitness 

2. Re-examination consultations 

2.1. Fractures of the spine 

2.1.1. Fractures of the dorsolumbar region 

2.1.2. Fractures of the cervical region 

2.2. Arthrosis 

2.3. Vertebral osteoarthritis 

2.4. Flheumatoid pelvispondy.lltls 

2.5. Surgical intervention 

2.6. The problem of repetition 

Study of the harmfulness of ejections and statistical /66 
analyses -.have objectively shown that the spinal column is 
placed under severe strain during the abandonment of distressed 
aircraft. 

It thus becomes necessary to determine the standards for 
fitness of the spine for the use of electable seats. 

These conditions for fitness are viewed in two very 
specific aspects: 

— fitness for -acceptance, of aircrew, 

— fitness during re-examination ..consultations and after 
aircraft accidents. 



1. Acceptance of Aircrew 

There are no commonly held views among NATO countries on 
whether or not a systematic radiological examination should 
be performed on the spinal column during admission examinations: 
of aircrewV 



61 



iQg 4vCa,X ■ ■ Exaini,n,at;.xQa ' 



Remarks 



USA'P 

U.;S. Army^ 

PAP 

GAP 

HAP 
lAF 
RAP 



Xes: (?) 

Yes 

Yes 

Yes 
Yes 

No 



Performed if there are 
anfc-e.cedenta. or If there 
J,5. reason, for clinical 
doubt 

To dete.ct spondylolysis 

or spondylolysthesis 

or if there are clinical 

standards 

Entire spine, admission 
only 

Entire spine (upon admis- 
sion and 5 years later) 

Dorsal and lumbar regions 

Entire spine 



1.1. Radiological Test of Fitness /67 

Currently all candidates for aircrew personnel in the PAP 
are required to undergo a radiological examination of the entire 
spine. 

This examination consists of seven x-rays taken at standard 
angles : 

— front and side views of the cervical region, 

— front and side views of the dorsal region, 

— front and side views of the lumbar region, 

— front view of L5. 

These x-rays are taken standing. Special care should be 
taken in positioning the subjectB. In some cases dynamic 
examination from the side is indispensable for studying the persis- 
tence of a congenital abnormality. 

The confidential interpretation Cnot communicated to the 
candidate) is extremely detailed- It must .contain all anatomic 
variants, and congenital abnormalities,- even those which are 
discrete..: 

This reference, file has- a threefold purpose: 

— elimination of serious injuries, capable ,of modifying 
the' strength of the vertebrae and Incompatible with 
flying practice* 



62 



— possifele Gompari^-Qn vtXtli x-rays; taken .after, tisaum^ 
Ce.Jectlon,. tlytrig accident,; et.c-. 1- 

These factors comprise- a. vXe-iitpotnt which. Is shared by 
specialists in other European air, forces. Some organizations ^ 
however, do. not consider radiological examination' of the 
spine a requlremeht, for the following reasons: 

— increased radiation doses for the aircrew, 

— low likelihood of the necessity- for ejection. 

In our opinion this position is not logical for the 
following reasons: 

— the existence of a large number of acquired diseases /68 
or congenital abnormalities without clinical 
manifestations , 

— the absence of a reference file, which is always use- 
ful in safeguarding the interests of the government 
and the pilots from a medicolegal standpoint, 

— lack of the opportunity for serious study of the occu- 
pational pathology of aircrews, 

— lack of information on the development of normal 
radiological Images. 

1.2. Standards of Normality 

Frequently regulations require that every aircrew candidate 
be in perfect clinical and radiological condition. The defini- 
tion of a normal spine, however, remains problematic. Some 
consideration should be given to this question since any fixed 
set of regulations produces the risk of eliminating too many 
candidates, since normality factors may themselves vary. 

In front view, the line of the spinous processes follows 
the vertical descent of the exte.rnal occipital protuberance 
to the tip of the coccyx. 

In side view, the vertical line; ^pas sing through the 
large trochant^er intersects LI or L2";at its midpoint and ends 
tangential to the anterior surface of theuatlas' and the axis 
Ct he ore tic ally normal posture). 



63 



. Vnts. <X^^XnX.tt:Qn. -seems: .to: .t!e::.*pa,rt-lGularly: valid, for examina- 
tion In dorg.al 4e.cut3ltus,' 

In standing position,- very^. ;Few .s.uba"ect&. meet , .. , 
tlies^e s^tandards:. 

Some Investigators- Cs-peclfically Testut,: Schmorl and Jung- 
hans)- donslder^tjie; frequent minimal dorgal inflection with 
right convexity to be a normal ■ . variation Cclassical 
normality) . 

Others consider it to be due to greater development of the 
trunk musculature on the right side, appearing at approximately 
age 6. Still others consider It due to the presence of the aorta. 

A study dealing with 2500 files of spinal x-rays performed 
from 1969 to 197)1 in the course of admission examinations for 
FAF aircrews has facilitated the study of normality and 
decisions as to fitness. 

TABLE 16. DISTRIBUTION OF SPINAL ABNORMALITIES FOUND IN A HOMO- 
GENEOUS FRENCH POPULATION AGED 19 TO 23 (French Air Force). 



1. Postural Disturbances 

a) Iti the frontal plane 

— scoliotic position 

— scoliosis without pelvic 
d sequilibrlum 

— scoliosis with pelvic 
d sequilibrlum 

b) In the cervical region 

— infleetloiji 

— d'ysharmony 

— dysharmony + inflection 

2. Anatomical Variations 

— Anterior cuneiform appearance 

LI 

L2 

D12 

Other vertebrae 

3." ' Sequels of :Scheuermann'a 'Eplphy-so^sls 



/69 



1867 


74.68^ 


518 


20.72SS 


839 


36.56^ 


510 


20.40^ 


471 


18.84$ 


J329 
95 
47 


13.16^ 
3.80^ 
1.885s 



191 

102 4.08; 

35 1.40J 

30 . 1.20; 
24 . 



302 



12.01 



64 



482 


19.82^ 


437 


17.48^ 


23. 




12 




2 




t . 




1 




1 




1 




4 . 





237 



9.48;? /70 



' 4'.. Co:n:gen.'Ji,f a;!; Ma^IfQ'mattQn 

a I DeliJ^sceace: of the pQsterioi;' arcti 

SI 

L5 
^2 

C5 

C6 

01 

Dl ■ .- 

CI, C2, C3 Crelated) 

Various 

b) Transitional abnormalities 

L5 

Hemlsacralization 

Sacralization 

Sacralization + Neoartlculatlon 
SI 

Heml lumbar Izat ion 

Lumb ar i s a t i o n 

g) Isthmlc lysis 

* With spondylolysthesis 

— of L5 on SI 

— of l4 on L5 

— of SI on S2 

— of C6 on C7 

* Without spondylolysthesis 
-- L5 

— l4 

— S2 

d) Congenital blocks (aside from transitional abnormalities) 

26 1.0k % 



37 


1.48;? 


52 


2.08^ 


20 


0.80;? 


26 


1.04^ 


102 


4.08;? 


114 


4.56^ 


76 


3.04;S 


68 


2.72 


4 




3 




1 




38 


1.52;? 


31 




4 




3 





- C2, C3 

- C3, c4 

- c4, C5 

- C5, c6 

- C6, C7 

- C7, Dl 

- D9, DiO 

- DlO, Dll 



10 

3 
1 

2 

2 
2 
2 



65 



■ el Raprer a,Un,opnia.ll;t4.es: ' ' {'IX 

—^ Anterior body' 28. 

--^ Anteriar retromarginal hernia ^^ 

— ^^ Outline .of cervical rib 9 ' 
— Detached nucleus; 

* Of spinous process of QZ . 1 
■ * Of spinous process, of C3 1 

* Of transverse process .of Dl 1 
. * Qf transverse process .of LI 4 

* Of transverse' process of L2 1 

* Of transverse process of L3 ' 1 

* Of transverse process of l4 . 1 

f) Klmmerle*s abnormality 

(arcual foramen) l62 6.48^ 

These extremely homogeneous statistics show the high 
frequency of spinal abnormalities. 

In addiitlon, they show that only a very low number of sub- 
jects meet the criteria for normality. 

As a result, and taking Into account the large number of 
spinal abnormalities with no actual or practical significance, 
the current definition of normality should be reconsidered. ■ 

1.3> Postural Disturbances. Broadened Definition of Normality /72 

Postural disturbances represent the- majority of recorded 
abnormalities. 

Postural disturbances in the -frontal plane: 1867 cases 
(74.68^) have been recorded. 

These are of two types: 

* scoliotic position, simple discrete lateral Inflection 
without rotation of the vertebral bodies, encountered 
in 518 cases C2Q..72;S); 

This falls within the framework .of classical normality. 

■ *• scoliosis ; There are 1349. cases of scoliosis, 839 of 

them G3^56^1 without disequilibrium of the pelvis, 
and 510 .C2a., 40.^.1 with pelvic disequilibrium. 



66 



- Bofcii c,a.se¥. U8'U^3,ly i;nY0.1ye. &llgh:.f scol^oats with minimal 
curya.ture aA(l-yery- cJlgc,?'ete. rotatlpn ;of tJie YeJ7-fee-bra,l .bo.dles. 
Th.ere Is no pain S-ymptf^ii^atQlogy-,- 

The growtli of the subjects: is. .completed and it does' not 
seem likely that the scoliosia will h^. iexacerhated Cespecially 
in cases- lower than 15°CI. 

Adopting the criteria of classical normality, there 
remain 13^9 subjects with scoliosis. 

It was difficult to accept that nearly 50%. of the subjects 
could be "abnormal." 

Normality should represent the majority of supposedly 
healthy subjects (according to Gaussian data). The maximum 
angle of scoliosis compatible with the conditions of ejection 
and piloting of combat aircraft is fixed at 15° j which cor- 
responds to USAP and GAP regulations. 

In the 2500 spines examined, the angle of scoliosis .was 
greater than 10*^ in only 5^^% of the cases. 

Cervical postural disturbances were frequent and wereT'.almost 
always extremely minimal (471 cases, 18.84^). 

These may be evaluated only on the basis of the x-ray views 
taken, under very rigorous' technical conditions. 

1.4. Fitness and Congenital Abnormdlitles /73 

Major congenital malformations with heavy clinical dis- 
turbances or obvious modifications in posture will not be 
considered. 

These unquestionably result in unfitness. 

Consideration will be given only to a given number of 
abnormalities which show no j clinical manifestations and are 
revealed only by x-ray examination. 

Some malformations which do not modify the strength of 
the spine should not resiait .in the' subject being designated 
unfit. 

Qthers: which show- risk of wea,kening the spine may be taken 
as-, disqualifying factors:: the subj.ect will be designated unfit 
only after study- .of the type of malformation and' its. . > ■ , 
site; in relation to. the' area likely to undergo trauma Cmedian 
dorsal region and dorsolumbar hinge, for combat aircraft pilots). 



67 



[Phe. .ol?4'e'^''< ^^ to. avoid disqualifying highly > m9ti.vated sub- 
jects-, w.hiie -etiJ,!. ren]ai.nlng within, noriiial. s.afety. .restrictions. 

I.' Pis-co's'omati^C "Abnorma.rit:ies- 

Cons-equen'ces- .of deveiopinental problems in the dorsal cord, 
these- result from defective segmentation and a vascularization 
disturbance.' 

When not fatal, these abnormalities^ entrain more or less 
severe deformations and disequilibria, 

* The eongenitai' vert'ebr'ai" block represents partial fusion 
of one or several vertebrae. 

An isolated problem, it does not result In any change in 
height or curvature. 

It most frequently appears in the form of a C2-C3 block 
and sacralization of L5 on SI. 

Injury to the cervical region is rare in aeronautical 
medicine. If the block is Isolated and is not accompanied by 
any modification of posture or the dynamics of the cervical 
region, the subject may still be designated fit. 

Identical principles hold for lumbar or dorsal sites. .. ; .-. /74 

Blocks of three vertebrae or more result:' in unfitness. 

* Vertebrae with cuneiform tendency , frequent variants 
(191 cases), are due to poor pressure distribution. 

These are found at the center of the natural cur- 
vatures (D6, D12, LI). 

In the opinion of Delmas, these are capable of alteringythe 
strength of the posterior wall. This observation is significant 
since these vertebrae are located in frequently injured zones,. 
The research undertaken has been too recent to formulate 
definitive conclusions. 

The subject is still deemed fit for service. 

*■ Lack of. "fusion of tKe vertebral' 'bodies . 

This infrequent abnormality. CI. 8^) indicates a develop- 
mental disturbance*' Normally, ^, .fusion takes place at 
approximately- 21 to 23 'years of age, and this configuration is 
normal in children. 



68 



JX t.^ :mQS.t, .freq;Ue-ntl.y. .found, .for a sing-le vertebral .body 

&oine ■J;nvest-;Ji:gators- cons-ider th;,at -th;is. abnormality, .even 
when Isolated, .will wealcen the disk and; .result .in precocious 
degener^t-ten. ' This- opinion is not -^Ixared by a large number 
of radiologists^' and rheuraatQlQgists-,' 

The subject .should be designated, fit. 

The problem' is different ■when the anterior body is 
associated with sequels^ of epiphysosis or anterior retromarginal 
hernias . 

* S'chmorT ' s furrows , due to abnormal discal expansion, are 
a cause of unfitness when they occur in multiple regions and 
are related to epJiphysosis sequels. 

An isolated Schmorl's furrow should not be an eliminating 
factor. 

* Anterior retromarginal hernia . This is a characteris- /75 
tic notch in the vertebral facet, generally the upper facet, 

of a dorsal or lumbar vertebra. 

It frequently accompanies sequels of epiphysosis, but ±t 
may also be isolated, which does not make the subject unfit 
for service. 

* Rare malformations: sagittal dehiscence of a vertebral 
body and supernumerary hemivertebrae are reason for unfitness . 

2. Abnormalities of the Posterior Arch 

These result from disturbances in the development of the 
neural canal. They may be accompanied by menlngeal-spinal cord 
malformations, but minor changes without clinical manifestations 
are frequent. 

* Isolated dehiscence of the pQste.riQr arch : The most 
frequent malformation {^ii2 cases, 19.iiZ%). 

This is frequently found at the lumbosacral hinge. 

This asymptomatic phenomenon does not change the solidity 
of'S^the spine. 

It should not be a, basis, fqr unfitnes-s' CPAF, HAF, GAF, lAF, 
U3AF1. 



69 



. *■ DgKj:;9:cerice' Qf ■ Xhs i&thjni; or ^spondylolysis . This .phenomenon, 
which Xs. :rela,tl,ye.ly^ freq,uent ,a,na Is.. ua:ually ■bllatejc'al, commonly 
Involves the last lumhaj;' verte.br.a.e,. 

In countries which require x-^rays: for admission, spondylo- 
lysis- is- a disqualifying factor. One 'may question whether this 
attitude Is- excessive.iy- severe;' In some.' cases spondylolysis does 
not develop, even if thei^e is discrete, spondylolysthesis, and 
after age 21 it generally remains static. 

3." Trah'sitional Abno'rm'alitles 

These are frdiquently observed. They are generally located 
at the level of the hinge zones'. 

There are basically two types of transitional abnormalities 
of the lumbosacral region: sacralization of L5 and lumbarlzation 
of SI. 

Sacralization of L5 Is an abnormal development of the trans- /76 
verse processes of L5, which tend to become articulated or unite 
with sacral wings. 

This more or less marked hypertrophy may be unilateral or 
bilateral. 

It does not result in unfitness. The lumbosacral hinge is 
not an area of possible trauma in ejections. 

Lumbarlzation of SI is manifested by the absence of sacral 
wings at the level of SI and the presence of long thin trans- 
verse processes coming Into contact with the iliac bones. 

Here again, the subject is customarily designated fit. 

1.5* Acquired Diseases and Fitness 

All acquired diseases of tuberculous osteoarthritic or 
or staphylococcic type, arthritis Crheumatoid pelvlspondylitis) 
and angiomas are eliminating factors. 

The U3AF permits acceptance with cured spinal fractures if 
the trauma has occurred more than 1 year earlier, if there is 
no symptomatology and if the height oX the vertebral body is 
compressed no more than 25.^. This position is not unanimously 
held, but in our opinion it is quite rational except in the .case ■ 
of ' cervical sites. 



70 



•geqiuel's; to: 3'cft"e.u'e'rjnajin^s:. ^Igt'esL's-e' ■.•Cspi.nal growth, dystrophy), 
"if they ^^ sJ:gnJ^f4.ca^t,, slxQUId Msa ,conai,de.rea' a 'basis for disquali- 
fication. Tlie: editgrg- tiave been very disturbed by the opinions of , 
of various organizations: most: consider these sequels ai^O- be 
disqualifyijTg ^'actors-.' In our- opinion,. ..some pf these sequels, 
which do not weaken the vertebral str^ucture. and do not' increase 
the' natural dorsal kyphosis, are. ;conipafc'tble with fitness . 

In conclusion, it .^'.appears- that the pos^itlons of specialists 
on this matter are to.o severe In disqualifying .-fighter pilots 
(fitness for electable seats). Ejection actually occurs very 
rarely in flying service, and some of the rules currently. In 
force as a function of . the number of . candidates and the needs of 
the organization may be made more flexible without additional 
spinal rigk. 

2. Re- examination Consultations /77 

Any injury may weaken the spine and sensitize it to the 
effects of various flight stress factors. Some of these factors 
are usual and Iriherent in flight (vlbrationv long-term accelera- 
tion), and others are accidental, such as ejection, first of 
all, or crashes, more seldom in occurrence, subjecting the 
skeleton of the pilot to considerable force applied for a very 
short period of time. The problem of continuing to designate 
aircrew personnel as fit or disqualifying these personnel ' 
occurs', after any medical or surgical spinal problem. 

The spinal column consists of a skeletal, llgamentary and 
muscular assembly extending from the head to the pelvis. It 
is a virtual organ with the functions of support, shock 
absorption, protection of the spinal cord by preserving the 
spinal roots in emergencies, and mobility, related to 
the relative stability of the respective relationships of 
the components of which it consists. 

This aspect of fitness Is thus very different from that of 
acceptance. There is no precise and typical line of procedure . 
Each patient Is a special case, and frequently decisions can 
be made only by medical and surgical collaboration. 

•2.1.- • Fractures of the' Spine 

These- ex.tremely. frequent spinal injuries occur as the 
result -.of. various traumas; highway accidents., aeronautical 
practice, sports-, Whate.ver th^lr etiology may be-, the problems 
of fitness posed by the existence of these injuries are identical 
and sometimes: extremely difficult tO: solve. , 



71 



z:z.X.- ■ •fraotUyesJ qT 'the DoTaQlum^'ar Heglon are Qt).e:e.rvea In 
a^rQrLa.ut<ical pract4;ce.. :Le4eciii.on, .especially paracMtljagi. • Tixey 
very. frequeAtly njQcJ.ify th.e soliaity :ot ttie spinal column, and 
the decistona to. be talcen depend on tHe, type of fracture. 

The fractures', fall into two classifications:' comminuted 
fracture and simple compressiQn fracture. 



Comminuted' -Fracture b'f tKe Doraoiumtiar 7'ertebrae 

A series' of, tjasic findings revealed by R. Watson^Jones 
should be reviewed. When the anterior edge of a vertebral body 
has penetrated a fractured body., the spine was In hyperflexlon 
at the moment of trauma. In these eases the Intersplnous 
ligaments are torn and the apophyslc or Interapophysic joints 
are frequently dislocated. The upper and sometimes lower 
disks are injured. These fractures are of unstable type. In 
the opinion of R. Watson-Jones, trauma producing an Isolated 
dislocation, compression of the bone, ruptured disks, torn 
ligaments, fractured pedicull, interartlcular dislocation, 
partial destruction of the anterior vertebral foramen or com- 
pression of the nerve roots will probably entrain the persistence 
of \ severe pain , . even . if . : \ the displacement is slight 
and reduction is maintained. These fractures are slow to heal. 
If conservative treatment is used, the patient should be kept 
flat for at least 6 months, sometimes 9 to 12 months. Syn- 
ostosis of the vertebral bodies and ossification around the 
articular processes appear only at a late stage. Pain, dis- 
comfort and a sensation of weakness will last a very long time. 
Functional cures of serious comminuted fractures are observed 
only after several years. 

This Is why an attempt is made to accelerate this cure by 
the use of surgical procedures encouraging the fusion of the 
spinous processes and the vertebral laminae. 

The decision for the specialist is simple: the in^iured 
subjects must be classified unfit for combat . -.i The spine is no 
longer capable of tolerating, without risk of injury, the 
constant stresses of flight, much less- -accidental' ■..,■..: 
trauma Caddltional ejection, crash) to the spinous processes 
and the vertebral laminae. In addition, these subjects fre- 
quently suffer even under normal day-to-day conditions, 
since arthrosis occurs- with a high frequency which varies with 
the statistics., considered C5.Q to 70^.). 

The same is true of f ra c.t ur e-^'djs lo c at ions , which should 
permanently disqualify, fighter pilots-, ' 



72 



■ SJ^pIe Campy es,:5j;Q,n Ji^.actUreg:^ ' ■ /79 

Tfie va,pta Quro^ ■.Qtjt.ained. j:,s a^lvrg^ye-. -facilitated' by the '■•■ ■ 
use of . exercisea-. a.d^pted to. the. clinical caae. The pilot ■■ 
may be authorize.d to return to. .service'. Xn a, short period of 
time due to the' effective aid of the flight surgeon, who 

carefully monitors the pilot's return .to. occupational activities 
which are frequently Intense 'Cca'se of combat pilots). Daily 
vertebral exercises^, indoctrination of. the aircrew, and possible 
psychological support always facilitate the operational activity 
of these pilots. HTere the flight, surgeon plays an essential, 
fundamental and irreplaceable role. There is now an awareness 
of the benign quality of simple compression fractures, which was 
not the case. 20 years ago. Overly. severe decisions are no longer 
necessary due to Improved knowledge-of the course of these, 
injuries. 

2.1.2. Fractures of the Cervical Region 

These are almost always due to highway accidents or 
athletic activity (especially diving). They frequently involve 
fracture-dislocations usually located at the level of the last 
five cervical vertebrae. More rarely, the atlas and the axis 
are injured. 

There is a general tendency to eliminate these subjects 
and to classify them permanently unfit for service as fighter 
pilots. These injuries should be examined by the most thorough 
means of radiological testing. Modern tomographs permitting 
sections down to 1 mm have made it possible to examine these 
injuries closely, and an attempt to determine their influence 
on cervical dynamics should always be made when possible. 

In cases of Isolated fractures of the lateral musculature 
of the atlas not entraining any marked postural modifications 
and without clinical repercussions, the reporting organizations 
have given qualified unfitness decisions in two cases, granting 
permission for flight in light aircraft. There has been no 
cause to regret these decisions, since the injuries were very 
specific and relatively rare. 

On the other hand, it has appeared to. us that not all cases /So 

of fracture>^dis.lo.^cat ion of the at la's-axis . even when treated ' 

surgically, h.ave permitted , continuation of fighter-pilot 
activities^.' 

' 'Xsolated fra'cfures' of the 'articular P'roce'sses: , which often 
go unrecognized in early ■radiological examinations-,- should result 
in less severe decisions, after study of the clinical and 



73 



j;'acllQaogic^l p.att.ej!,n Cp.a.rt4;Qulegrly ayna^nlc examination) and 
.properly conduQte.d ^retxatjllltatlon. This la- a typical example 
of. graduate-d: d^clalons'. W the :s,peclallst-,. who' should- synthesize 
the. varlQus- medical and psychological .e-lements. and weigh the 
Interests: af the aj?med; forces against thoae of the Individual. 



2.:i.3.' ■ -Fx^'acfurea- of tKe Tran's:Ve'r:s-e^ 'Pr:oce's:s:es of the lumbar 
vertehrae ,■ frequently multiple, and extremely painful, should 
permit the pursuit :of normal aeronautic activity after treat- 
ment and rehabilitation of the mus-culature.' 

2.1.4'.' Trauma vrlthouf Fracture 

The absence of radiological lesions does not signify the 
absence of anatomic lesions of the intervertebral disks and 
the ligaments. The onset of pain or degeneration of the disks 
in the years following ejection or trauma is always possible. 
In cases of pilots who have continued to fly, it Is frequently 
extremely difficult to determine the part played by the trauma 
Incurred- lin ejection. Radiological tests 2 to 3 years after 
the accident are always useful for comparing the development 
of the vertebral condition In time and for detecting the onset 
of arthrosis. This difficult problem, which is being studied 
under the auspices of the AGARD,^shows that It may be presumptuous 
to attempt to fix management procedure over a period of years, 
in view of the development of radiological techniques and 
changes In flying procedure. 

2.2. Arthrosis (non- traumatic) 

Isolated arthrosis , which frequently shows no clinical 
manifestations but is sometimes revealed by acceleration (aerial 
acrobatics), usually only necessitates bedrest. Moreover, 
there is no parallel relationship between radiological lesions 
and the clinical repercussions of arthrosis. Its preaence 
rarely resulta In unfitness for service. 

The course of arthrosis affecting several intervertebral /8l 
areas Is fairly frequently marked by outbreaks of pain. Decisions 
of provisional unfitness facilitate the Implementation of rational 
therapy Crest, medication, followed by muscular rehabilitation). 
It should be recognized that this type of arthrosis occurs most 
frequently toward age 4Q.,. which decreases the likelihood- of its 
occurrence ■, in fighter pilots.. 



74 



' 2.3. '. yer^ti.etj.ra,'! Q:s::te:Qa,rtlirj;tts 

. a,! The presence, pf tub'erculolta .;o;s.'feo'a'rth:r"l'tls :of the 
spine 'CJ.Q.tt-^s-. disease I ts' refetlvely ea,sy to: define. In all 
the organizations responding to the .q.ues'tlonnaire,' this, disease 
is a dls-q^uallfying factor for ■ acceptance of flying personnel. 
Since radlologlcai examination of the. spinal column was intro- 
duced as a requirement in the admission examination, no cases 
of Potf's disease have been observed. 

The decision to Judge active flying personnel permanently 
unfit for service will he taken not. for functional reasons » 
but due to the presence of a tuberculous infection which 
always may ' appear, despite the use of effective 

medication. 

The observation of a number of cases of tuberculous 
osteoarthritis in general practice, in non-aircrew subjects, 
has permitted us to formulate a very definite opinion. There 
can be no question of permitting continued aeronautic activity, 
even after non-mutilating medical treatment or limited 
surgical treatment. In our opinion, the only logical decision 
Is to designate the pilot as permanently unfit, no matter what 
his length of service, experience and value may be. 

b) Other types of osteoarthritis (melltococclc, staphylo - 
coccic) deserve special attention. All these types have little 
destructive effect on the vertebral bodies and have a tendency 
to produce ankylosis In a very short period of time. Here exper- 
ience in regard to aeronautlce practice is lacking. However, 
we have been able to confirm that once the spine has healed 
there Is no unusual weakness. These opinions, of course, should 
always rest on a complete analysis of the clinical, laboratory 
and radiological pattern. We believe that in certain cases 
the pilot may still be deemed fit, taking into account the site 
and severity of the lesions observed. 

2 A. Rheumatoid Pelvispondylltls Cankylosive spondylarthritis) /82 

These lesions are located at the level of the sacroiliac 
vertebrae and the dorso lumbar hinge. The movement capability 
of the spine, which Is preserved at the beginning, gradually 
decreases: as a function of the onset of rheumatoid att.acks. 
An attempt should also be made to determine other sites ■ . . - , 
which will have, an Inf luence:-;on;,>the prognosis and the decision 
as to, fitness: 

— -sites in the' respiratory tract with Ventilatory 
deficiency of. .restrictive, type, linked, to. lesions of the 
costal-transverse Joints, and revealed by. functional 
pulmonary testing i 

75 



^- ca,rdi,a,c ' '-sites: . YV.vX&.^pe^&~- :of. valvular, cardiopathy, 

the jijQSt; .freq^uent- ;of ti^hlch.' are aortic .■d,.eflclency, .dls- 
turtnancee ;L.n, .auricular-ventricular conduction, .and 
rhythmic disturbances^; 

— ocular sites (Iritis). ' ■ ■ 

This chronic disease is; us-ually. compatib.le with appreciably 
normal aeronautic activity, for a given length of time, with the 
help of carefully controlled treatment. The therapeutic method 
primarily combines vertebral and respiratory klnesitherapy 
and medication Cacetylsalicylic acid and derivatives). 

The decision as t6. -the pilot's fitness should take into 
account the fact that this is a chronic disease which is sup- 
pressed for long-.>perlods by a non-dangerous treatment and is 
compatible with appreciably normal aeronautic activity (R. Pannier). 

The onset of ankylosive spondylarthritis during a pilot 'is 
period of service leads to a much more complex policy, deter^' 
mined by various factors: 

— the ■ course :of the disease, which varies from one 
subject to the next, 

— the degree of functional impairment resulting from 
stiffening of the spine, 

— the existence of valvular cardiac lesions, electrocardio- 
graphic abnormalities, or ventilatory deficiency, 

— the necessity of using major inflammatory medication, 
exposing the subject to digestive complications. 

A combat aircraft pilot may be retained as fit for an /83 
extremely variable length of time depending on the course of 
the disease, klnesitherapy and the effects of medication; when 
the stage of complications is reached, the subject should be 
considered unfit. 

2.5. Surgical Intervention 

1. Lamlhectomy 

Th.e' purpose of this surgical operation, which is performed 
only after careful consideration and in s.p.ecial cases', is to 
explore or decompress the spinal cord. It is followed by- a 
high degree: ;of Instability, .which will be increased to the ' 



76 



4egr.Q,e that Xt i.n,yQ.Xye.s-. s-.eyeral laminae aad is. ex.teaded laterally 
la tfie cilj'eQt.l.Qf; .Qf the articular p.po.ce&aes , Laminectomy :Ccom- 
pres-alon. ojf th.e^ s;plnal cord-, tumor I may in Itself provide a 
reason i*or' permanent unfitness-. 

In our opinion, flying personnel should .be Judged com- 
plete l^r and permanently unfit for service after a laminectomy. 
There appears to be too great a risk: In the course of aeEonautic 
service of additional trauma to. a s-plnal column vrhlch has already 
been weakened, 

2. Cure' of Dlscal' Hernia 

This Is an operation which In most cases does not pro- 
foundly affect the solidity of the spine. Before making a 
decision, specialists should carefully analyze the contents 
of the operative report and should base their decision on the 
results of the clinical and radiological examinations* They 
should require that the operation involve only 
minimal laminectomy, that the diagnosis of discal hernia 
be confirmed, and that there has been satisfactory cur- 
ettage of the intervertebral disk. There should be perfect 
clinical results with restitutio ad integrum. In particular, 
there should be no residual paresthesia or persistent pain. 
Tomographs should reveal remaining lesions of satisfactory 
appearance. 

In our opinion, if there is considerable damage to the 
bones or ligaunents , the pilot should be judged unfit for combat 
service. If the ablation of the discal hernia meets the 
previously described criteria, in some cases complete fitness 
may be maintained, 

2.6. The Problem of Repetition of ejections for a single combat /84 
aircraft pilot should be mentioned, but the number of cases 
observed remains too low to permit any general opinion. Study 
of this repetition of trauma is extremely interesting. So far 
it has been found that spinal fracture never recurs at the same 
vertebra, if there are no radical changes in posture. These 
cases should be combined for an overall study. 

In CQhclusl.Qn 

It Is impossible to. typify fitnes-s: criteria in cases of 
spinal lesion, .except, for. a, few o.bVlous cases,' The approach 
which, we have. Just outlined reflects: the current positions 



77 



genera,Xi,y^ 4ef-^ri,<iQd lay' specl.aXis-fs- in vaji'ious. cQuifitriea, 
Ti:i.eae; pQSi3;tl.QA3 .i^ust aXwa,ys be adapted to- the 'specific clinical 
and psycho logical ca,3e.' Collaborating physiclanB, radiologists 
and surgean.s- should carefully .T^eighi.' th.e risks incurred and 
faithfulness- to the interests of the aircrew and the armed 
forces.' The problem of fitness- criteria will change over a 
period of time, since surgical advances; and new aeronautical 
procedures' must' be taken into, account.: 

Editors' Recommendations /95 

The editors believe that spinal fractures occurring after 
ejection constitute an important chapter in aeronautic medicine, 
whose study should be pursued over the next few years. In 
actuality, the use of new equipment may modify some of the find- 
ings studied in detail in this report. It is hoped that in a 
few years a working group will resume study of these frequent 
injuries to fighter pilots. 

— We recommend the systematic performance of x-rays of the 
spine immediately after ejeiction, no matter what the symptomatOTii.- '• 
logy may be. 

— j-^ would. ..be desirable to ■ formulate -uniform selection 
criteria. In general, the editors consider, a 

given number of slight abnormalities (spondylolysis, for example) 
to be compatible with ejection. Attention Is drawn to the 
excessive severity of some fitness criteria. 

— It is our opinion that experimental studies should be 
pursued to obtain improved positioning of the pilot in the 
seat and to attempt to determine physiopathologenic mechanisms, 
especially in complex aircraft escape. 



78 



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